Chess

Chess
	From left, a white king, black rook and queen, white pawn, black knight, and white bishop in a set of Staunton chess pieces.
Players	2
Setup time	10–60 seconds
Playing time	1 minute - 7 hours*
Chance	None
Skills	Tactics, Strategy
	Games by correspondence may last much longer;

Chess is an abstract strategy board game and mental sport for two players. The object of the game is to checkmate the opponent's king. This occurs when the king is under immediate attack (in check) and there is no way to prevent it from being captured on the next move.

Chess is one of the world's most popular board games; it is played both recreationally and competitively in clubs, tournaments, online, and by mail or e-mail (correspondence chess).

Many variants and relatives of chess are played throughout the world. The most popular, in descending order by number of players, are xiangqi in China, shogi in Japan, janggi in Korea, and makruk in Thailand. The game described in this article is sometimes known as FIDE Chess, Western Chess or International Chess to distinguish it from other variants.

Gameplay

Overview of the game

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The position of the pieces at the start of a game of chess.

Chess is played on a square board of 8 rows (called ranks) and 8 columns (called files) of squares. The 64 squares' colors alternate between light and dark, and are referred to as "light squares" and "dark squares".

Each player begins the game with 16 pieces which can move in defined directions, and in some instances, limited range, and can remove (capture) other pieces from the board: each player's pieces comprise 8 pawns, 2 knights, 2 bishops, 2 rooks, 1 queen and 1 king. One player controls the white pieces and the other player controls the black pieces; the player that controls white is always the first player to move. The players alternate moving one piece at a time (with one important exception) to either an unoccupied square, or one occupied by an opponent's piece, capturing it; with one rare exception, all pieces capture opponent's pieces by moving to the square that the opponent's piece occupies.

When a king is directly threatened with capture by one or more of the opponent's pieces, the player is said to be in check. When in check, only moves that remove the threat of the king's capture are permitted. The object of the game is to checkmate the opponent; this occurs when the opponent's king is in check, and no move can be made that would subsequently prevent the king's capture. Normally a checkmate will require the cooperation of several pieces, but can also be achieved with one. A player who deems checkmate is inevitable may concede the game (resign) to the other player. A drawn result (a tie) is also possible.

Chess has been described not only as a game but also as an art, a science, and a sport. It is sometimes seen as an abstract war game; as a "mental martial art", and teaching chess has been advocated as a way of enhancing mental prowess.

Rules of chess

Main article: Rules of chess

Name	Letter	Picture
Pawn	P
Knight	N
Bishop	B
Rook	R
Queen	Q
King	K

When a game begins, one player controls the sixteen white pieces while the other uses the sixteen black pieces. The colors are chosen either by a friendly agreement, by a game of chance such as pick-a-hand, or by a tournament director. The first player, referred to as White, always moves first and therefore has a slight advantage over the second player, referred to as Black. The chessboard is placed so that each player has a white square in the near right hand corner, and the pieces are set out as shown in the diagram, with each queen on a square that matches its color.

Each kind of chess piece moves a different way. The rook (colloquially known as a "castle") moves any number of vacant spaces vertically or horizontally, while the bishop moves any number of vacant spaces in any direction diagonally (meaning a bishop will always remain on the same color; note that each side has a bishop for each colored square, and between them they cover the whole board. Losing one bishop often creates weaknesses on the same colored square as the lost bishop). The queen is a combination of the rook and bishop (it can move any number of spaces diagonally, horizontally, or vertically). The king can move only one square horizontally, vertically, or diagonally except when a player castles. The knight can jump over occupied squares and moves two spaces horizontally and one space vertically (or vice versa), making an L shape; a knight in the middle of the board has eight squares to which it can move. Note that every time a knight moves, it changes square color.

With the exception of the knight, pieces cannot jump over each other. One's own pieces ("friendly pieces") cannot be passed if they are in the line of movement, and a friendly piece can never replace another friendly piece. Enemy pieces cannot be passed, but they can be "captured". When a piece is captured (or taken), the attacking piece replaces the enemy piece on its square (en passant being the only exception). The king cannot be captured in regular chess, only put in check. If a player is unable to get the king out of check, checkmate results, with the loss of the game.

Pawns are the only pieces that capture differently than they move. They can capture an enemy piece on either of the two spaces adjacent to the space in front of them (i.e., the two squares diagonally in front of them), but cannot move to these spaces if they are vacant. Conversely, a pawn can move forward one square, but only if that square is unoccupied; a pawn can move two squares forward, but only if it has not moved yet, and both squares are empty. When such an initial two square advance is made that puts that pawn horizontally adjacent to an opponent's pawn, the opponent's pawn can capture that pawn ("en passant") as if it moved forward only one square rather than two, and only on the immediately subsequent move. A pawn cannot move backward. If a pawn advances all the way to the eighth rank, it is then promoted (converted) to any other piece of the player's color, except a King or another pawn — in practice, the pawn is almost always promoted to a queen.

Chess games do not have to end in checkmate- either player may resign if the situation looks hopeless. Games also may end in a draw (tie). A draw can occur in several situations, including draw by agreement, draw by impossibility of checkmate (usually because of insufficient material to checkmate), stalemate, threefold repetition, or the fifty move rule.

Until the 1970s, at least in English-speaking countries, chess games were recorded and published using descriptive chess notation. This has been supplanted by the more compact algebraic chess notation. Several notations have emerged, based upon algebraic chess notation, for recording chess games in a format suitable for computer processing. Of these, Portable Game Notation (PGN) is the most common. Apart from recording games, there is also a notation known as Forsyth-Edwards Notation for recording specific positions. This is useful for adjourning a game to resume later or for conveying chess problem positions without a diagram.

Sample game

A sample chess game is made to help understand how to play chess and its rules. It explains chess through a simple demonstration, move after move. Please read this sample chess game for details.

Strategy and tactics

Main article: Chess strategy and tactics

Chess openings are a sequence of moves, often memorized, which will help a player build up his position and prepare for the middlegame. Openings are often designed to take hold of the center of the board (e4, e5, d4 and d5), develop pieces, protect the king, and create a strong pawn structure. The Classical School of chess expounds the virtues of occupying the center early using pawns and/or pieces, while Hypermodernism advocates the control of the center not by using pawns but with distant pieces. It is often important for a player to castle (a special move that moves the king from the center of the board two squares towards one of the corners) to protect the king. While studying openings can greatly improve one's results, it is important to understand the underlying reasons for each sequence of moves in an opening. This can greatly reduce the need to rely on rote memorization of the opening phase of the game. Of the utmost importance in the opening is maintaining balance, or equality.

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The black knight on e6 is pinned to its king by the white bishop, and the white knight is pinned to the queen on b1 by the black rook. Note that the knight on b4 is still free to legally move, while the knight on e6 cannot legally move.

When taking and trading pieces, the chess piece point values become important. Valuations differ slightly from book to book, but generally, queens are worth 9 points, rooks are worth 5, bishops and knights are worth 3, and pawns are worth 1. Since the king's loss ends the game, it is invaluable. Although, in the endgame, when there are few pieces left on the board and there is little danger of checkmate, the fighting worth of the king is about 4. The actual value and importance of a piece will vary based upon its position and the stage of the game. If a player performs a sacrifice (e.g. exchange sacrifice), he is choosing to ignore the standard valuation of his pieces for positional or tactical gains. The beginning player should be aware that points are not an inherent part of the game; there is no scoring and chess was played long before the idea of assigning points to pieces. Instead, points are used by a player to consider whether he will come out materially better than his opponent in an exchange of pieces. For instance, to lose two pawns (2 points) in taking the opponent's knight (3 points) puts one ahead in material by one point. Such an advantageous exchange of pieces may, however, be a poor tactic if it leaves the opponent with an exploitable advantage in the way the pieces are positioned on the board.

Chess combinations and traps do not appear out of thin air. Usually they are present because the opponent has certain weaknesses in his position. These types of "weaknesses" include: pinned pieces, overloaded pieces, weaknesses around the opponent's king, weak squares, unprotected pieces, weak color complexes, pieces not able to come back to defend the king, etc. The "weaknesses" can then be exploited with a chess combination that is often built out of a number of tactical "methods". Such weaknesses are often created in the opponent's position in the first place by threats, provocative moves, and generally strong "positional play", etc.

Chess combinations often include a number of types of tactic "methods" which many middlegame books classify and provide examples of. Such common "methods" include pins, forks, skewers, discovered attacks (especially checks), zwischenzugs, deflections, decoys, sacrifices, forcing moves, undermining, overloading, interference and even "quiet moves".

A fork is a situation where a piece is moved such that it attacks (forks) two other pieces simultaneously. It usually is difficult for the other player to protect both of his pieces in one move. Pins are used to prevent the movement of an enemy piece by threatening any pieces behind it should it move. Skewers are a kind of reverse pin where the more valuable piece is placed in front of a less important one. A discovered attack (or revealed threat) is where the movement of one piece reveals a formerly blocked line of attack for another piece of the same color. For clarification, it should be noted that a "pin" is a tactical "method"-the act of pinning the opponent's pieces. But a "pinned piece" is a specific type of weakness in the opponent's position, which when identified, can be exploited with a tactical combination.

A few common positional elements which high level chess players routinely must assess include pawn structure, king safety, space, and control of key squares and groups of squares (e.g. diagonals, open-files, dark or light squares, etc.). In addition, there are factors such as the two bishops that compensate each other's weaknesses. Most middlegame books recommend that once an assessment of the elements of the position has taken place, it is then recommended to try and form a "plan" to create an advantage. Once a plan is formulated, it is then recommended to try and ensure the plan is feasible through the process of checking concrete variations.

Great chess writer Aron Nimzowitsch outlined in the classic work My System a number of middlegame positional principles such as "rook on the 7th rank", "undermining the pawn chain", "restrain, blockade and destroy". This work has influenced generations of modern chess players in how they think in the middlegame.

During the endgame, pawns and kings become relatively more powerful pieces as both sides often try to promote their pawns. If one player has a large material advantage, checkmate may happen quickly in the endgame. If the game is relatively even, endgame tablebases and endgame study are essential. Controlling the tempo (time used by each move) becomes especially important when fewer pieces are left on the board. In some cases, a player will have a material advantage, but will not have enough material to force a checkmate. In this case, the game is considered a draw by insufficient material.

Alternative ways to play chess

Blitz chess is a version of chess where a chess clock is used to limit the time control for each player. Generally each side has three to fifteen minutes (five is common) for all of its moves. An even faster version of chess is known as bullet chess or lightning chess. Bullet chess's time controls are less than three minutes. Speed chess requires the player to spend less time thinking because if the player's time runs out, he loses. When playing at a faster time, computers become relatively more powerful than humans. If both players use computers to enhance their strength, it is called advanced chess.

When two players are separated by great distances they can still play chess. Correspondence chess is chess played through the mail, e-mail or special correspondence chess servers. Today, chess is often played on the internet through the telnet-based hosts (such as ICC and FICS) and TCP/IP based servers (such as Playchess and WCN), listed below.

Chess can also be played blindfold. In this case the play is conducted without the players having sight of the positions of the pieces, or any physical contact with them. Moves are communicated via chess notation. Some very strong chess players are able to play multiple blindfold games simultaneously.

Chess boxing is a hybrid sport which alternates rounds of boxing with (short) sessions of chess.

Chess variants

Main article: Chess variant

Chess variants are forms of chess where the game is played with a different board, special fairy pieces or different rules. The number of possible chess variants is unlimited. D.B. Pritchard, the author of Encyclopedia of Chess Variants, estimates that there are more than two thousand chess variants, confining the number to published ones.

Many chess grandmasters played chess variants and some even invented new ones. José Raúl Capablanca feared a "draw death" of chess and suggested making the board larger and adding new pieces, such as a combination of rook and knight and also a combination of bishop and knight. He played a number of test games and finally setlled on an 8x10 chess variant, Capablanca chess.

Bobby Fischer objected to the overemphasis on memorized chess openings in normal chess and invented a chess variant in response. In this chess variant, originally called Fischer Random Chess but now typically called Chess960, the initial position is selected randomly before each game. This random positioning makes it impossible to prepare the opening play in advance.

There are many more chess variants, like Suicide chess, where the goal of the game is to lose all of one's pieces and if a piece can be taken, it must be taken by the opposing side. Very popular between chess players is also Bughouse chess, in which two teams of players play against each other and give captured pieces to their partner. To speed up the game, one can play Marseillais chess, where two moves are made per turn. Even faster chess variant is Progressive chess, where the number of pieces one can move increases each turn (i.e. white moves one piece, black moves two, white moves three, black moves four etc.). In Atomic chess, not only is the captured piece removed from the board after the capture, but also the capturing piece and every other piece of both players, positioned in any adjacent square to that of the capture.

In the context of chess problems, chess variants are called fantasy chess, heterodox chess or fairy chess. Some chess variants are used only in chess composition and not for playing.

History

Origins of chess

Main article: Origins of chess

Many countries claim to have invented chess in some incipient form. The most commonly held view is that chess originated in India, since the Arabic, Persian, Greek, Portuguese and Spanish words for chess are all derived from the Sanskrit game Chaturanga. In addition, in the past only India had all three animals, horse, camel and elephant, in its cavalry, which represent knight, bishop and rook in chess. The present version of chess played throughout the world ultimately derives from a version of Chaturanga that was played in India around the 6th century. It is believed that the Persians subsequently created a more recognizable version of the game called Shatranj.

Another theory exists that chess arose from the similar game of Xiangqi (Chinese chess), or at least a predecessor thereof, existing in China since the 2nd century BC. Scholars who have favored this theory include Joseph Needham and David H. Li.

Chess eventually spread westward to Europe and eastward as far as Japan, spawning variants as it went. The game spread throughout the Islamic world after the Muslim conquest of Persia. When it entered the Islamic world, the names of its pieces largely retained their Persian forms but its name became shatranj, which continued in Spanish as ajedrez and in Greek as zatrikion, but in most of Europe it was replaced by versions of the Persian word shāh = "king". There is a theory that this name replacement happened because, before the game of chess came to Europe, merchants coming to Europe brought ornamental chess kings as curiosities and with them their name shāh, which Europeans mispronounced in various ways.

Chess eventually reached Russia via Mongolia, where it was played at the beginning of the 7th century. It was introduced into the Iberian Peninsula by the Moors in the 10th century, and described in a famous 13th century manuscript covering chess, backgammon, and dice named the Libro de los juegos. The entrance of chess into Europe is marked by changes to the rules, including changes to the moves of the bishops, pawns and queen, with the modern form emerging in the 19th century.

Origins of chess terms

Checkmate: This is the English rendition of shāh māt, which is Persian for "the king is finished".
Rook: From Sanskrit Rath which means "chariot", or Persian rukh which means "chariot" or "cheek" (part of the face). The piece resembles a siege tower. It is also believed to be named after the mythical Persian bird of great power called the roc. In India, the piece is more popularly called haathi, which means "elephant".
Bishop: From the Persian pīl ("the elephant"), but in Europe and the western part of the Islamic world people knew little or nothing about elephants (curiously, in Russia this piece is called slon, which is Russian for "elephant"). The name of the chessman entered Western Europe as Latin alfinus, a meaningless word that then evolved further (in Spanish, for example, it evolved to the name "alfil"); alfil is actually Arabic for "the elephant", where al means "the" and fil means "elephant". The Spanish word would most certainly have been taken from the Islamic provinces of Spain. The English name "bishop" is inspired by the conventional shape of the piece originally intended as the tusk of an elephant but which also looks like the mitre of a bishop.
Queen: Persian farzīn ("vizier") became Arabic firzān, which entered western European languages in such forms as alfferza and fers, but was later replaced by "queen". "Fers" (Ферзь) persists as a commonly-used alternate name for the piece in Russia.

Development of modern chess rules and pieces

Early on, the pieces in European chess had limited movement; bishops could only move by jumping exactly two spaces diagonally (similar to the elephant in xiangqi), the queen could move only one space diagonally, pawns could not move two spaces on their first move, and there was no castling.

By the end of the 15th century, the modern rules for the basic moves had been adopted from Italy: pawns gained the option of moving two squares on their first move and the en passant capture therewith, bishops acquired their modern move, and the queen was made the most powerful piece; consequently modern chess was referred to as "Queen's Chess" or "Mad Queen Chess". The game in Europe since that time has been almost the same as is played today. The current rules were finalized in the early 19th century, except for the exact conditions for a draw.

The most popular piece design, the "Staunton" set, was created by Nathaniel Cook in 1849, endorsed by Howard Staunton (a leading player of the time), and manufactured originally by Jaques of London. The style was officially adopted by Fédération Internationale des Échecs (FIDE) in 1924.

Organization of chess

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Chess congress

Main article: Fédération Internationale des Échecs

Chess is an organized sport with structured international and national leagues, tournaments and congresses. Chess's international governing body is FIDE (Fédération Internationale des Échecs), which has presided over the world championship matches for decades. Most countries of the world have a national chess organization as well. To join FIDE a fee must be paid that will enable you to be registered on the chess players directory.

FIDE is a member of the International Olympic Committee (IOC), but the game of chess has not ever been part of the Olympic Summer or Winter Games. Chess does have its own Olympiad, held every two years as a team event. The 2006 edition was held in Turin, Italy at the same venue as the speed skating competitions of the 2006 Winter Olympics. Armenia won the gold in the men's event, and Ukraine took the top medal for the women.

In order to rank players, FIDE uses the Elo rating system developed by Professor Arpad Elo.

Important chess competitions

For most, the ultimate chess competition is the World Chess Championship. From 1993 to 2006, there was no consensus on who owned the title. Vladimir Kramnik was World Champion by natural succession (having defeated the last undisputed World Champion Garry Kasparov in a match, and not having lost a match since), while Veselin Topalov was the official FIDE World Champion, having won the FIDE World Chess Championship 2005. In April 2006 it was announced that these two would play a match to decide a unified title from 21 September to 13 October 2006. Kramnik won this unification match by scoring 2.5-1.5 in a series of four rapidplay tie-break games after the score was tied at 6-6 following the classical time controls. The World Champion is not necessarily the highest-rated player in the world. Topalov is in fact rated number one on the current FIDE rating list.

The traditional way in which FIDE arrived at contenders to play the world champion was by means of a long drawn out series of qualification stages. Zonal competitions provided qualifiers for the Interzonal tournament(s) and the highest placed finishers in these contests competed in the Candidates Tournament, effectively a series of knockout matches to produce an eventual winner and challenger for the incumbent champion. Nowadays, zonal qualifiers join the world's elite players in a single knockout tournament, the winner becoming the new champion.

In women's chess, the world's highest rated female player Judit Polgar has never participated in the Women's World Chess Championship, instead preferring to compete with the leading men on what is commonly regarded as the elite tournament circuit. Older sister Zsuzsa Polgar is also a very strong player and was Women's World Champion from 1996-1999. The reigning Women's World Champion is Xu Yuhua, from China.

Other competitions for individuals include the World Junior Chess Championship, the European Individual Championship and the National Chess Championships of countries around the world. On the invitational or 'elite' tournament circuit, Spain's Linares chess tournament is undoubtedly one of the world's finest. Sometimes described as the 'Wimbledon' of chess, it is very popular with the world's leading grandmasters. Popular too, are Monte Carlo's Melody Amber tournament, the Dortmund Sparkassen Chess Meeting and Wijk aan Zee's Corus chess tournament.

Regular team chess events include the Chess Olympiad and European Team Championship. In view of the longstanding Soviet domination of these events, highly publicised and prestigious Russia (USSR) vs Rest of the World matches were arranged in 1970, 1984 and 2002 to provide a sterner challenge to Russian hegemony.

The World Chess Solving Championship is both a team and an individual event.

Computer chess

Main article: Computer chess

Serious work on machines that play chess has been going on since 1890 ^{[citation needed]}, and chess-playing computer programs featured prominently in the artificial intelligence boom of the 1950s - 1970s. At first considered only a curiosity, the best chess playing programs — like Shredder, Fritz etc. — have become extremely strong players. In blitz chess, they can beat the best human players; at regular time controls, however, battles between the very best chess programs and the very best human players have been tantalizingly finely balanced. However, it is important to note that the method by which computer programs play chess does not really resemble the way humans play chess — the computer simply calculates the board position after every possible combination of legal moves and acts accordingly, whereas human masters act more from intuition and pattern recognition. Moreover, as CPU speed and memory become less expensive, computer chess programs can search ever larger numbers of moves in the same amount of time, and store ever larger databases of opening and endgame positions. Nor has the study of chess proven particularly useful in the broader AI field; the methods used to play high-level chess are very different to the ones used for machine learning, machine vision, and the like.

The Association for Computing Machinery (ACM) held the first major chess tournament for computers, the 1st United States Computer Chess Championship, in September 1970. CHESS 3.0, a chess program from Northwestern University, won the championship.

Garry Kasparov, then ranked number one in the world, played a six-game match against IBM's chess computer Deep Blue in February 1996. Deep Blue shocked the world by winning the first game in Deep Blue - Kasparov, 1996, Game 1, but Kasparov convincingly won the match by winning three games and drawing two.

The six-game rematch in May 1997 was won by the machine (informally dubbed Deeper Blue) which was subsequently retired by IBM. Controversies arose after the match when Kasparov accused IBM of using human intervention, which IBM denied. It has often been claimed that IBM withheld the computer logs showing Deep Blue's "thinking" but in fact the logs were published shortly after the end of the match.

In October 2002, Vladimir Kramnik drew in an eight-game match with the computer program Deep Fritz. In 2003, Kasparov drew both a six-game match with the computer program Deep Junior in February, and a four-game match against X3D Fritz in November.

The chess machine Hydra is the intellectual descendant of Deep Blue; and appears to be somewhat stronger than Deep Blue was. Certainly it is very much comparable in terms of positions analysed per second. Given the relative ease with which it beats the other programs, and the humans it has met, Hydra may be expected to beat any unaided human player in match play. In June 2005, Hydra scored a decisive victory over the then 7th ranked GM Michael Adams winning five games and drawing one game in a six game match. Whilst too few games have been played to establish this, and neither Kramnik or Kasparov have played Hydra, Hydra's creators estimate its rating should be over 3000.

Kasparov's loss to Deep Blue has inspired the creation of chess variants in which human intelligence can still overpower computer calculation. In particular Arimaa, which is played upon a standard 8×8 chessboard, is a game at which humans can beat the best efforts of programmers so far, even at fast time controls.

References

Hooper, David and Whyld, Kenneth (1992). The Oxford Companion to Chess, 2nd Edition. Oxford University Press. ISBN 0-19-866164-9.{{cite book}}: CS1 maint: multiple names: authors list (link)
- Reprint: (1996) ISBN 0-19-280049-3
Mason, James (1947). The Art of Chess. Dover Publications. ISBN 0486204634. (see the included supplement, "How Do You Play Chess")
Rizzitano, James (2004). Understanding Your Chess. Gambit Publications. ISBN 1-904600-07-7.
Tarrasch, Siegbert (1994). The Game of Chess. Algebraic Edition. Hays Publishing. ISBN 1-880673-94-0.
Wolff, Patrick (1991). The Complete Idiot's Guide to Chess, 3rd Edition. Alpha Books. ISBN 1-59257-316-9.

External links

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Learning chess

Wikichess - Open chess repertoire project, chess openings explained and related by players.
Chess Glossary - Glossary of important chess terms
Learn to Play Chess - Chess tutorials for beginning and intermediate players.
ChessIndex.com - covers chess rules, strategy and history.
Official FIDE rules
Chess.FM - annotated grandmaster games and tutorials
How to Play Chess - for Beginners and Parents.
Exeter chess club - British club website with an impressive amount of information and tutorials. Here the whole site can be downloaded via FTP.

Chess news

Collections of games

Chess News- It's all about chess Regularly updated news
Chess Game Collection - Over 500,000 chess games in pgn format
Chess-Database.com - online chess database
ChessGames.com - online chess database and community
Chess Mix Database - a rich source for chess games from the latest tournaments, publishes every 10 days
ChessBase online database - games are filtered by year, player, opening, etc..
University of Pittsburgh Chess Page - medium pgn collection including world championship games, miniatures, and traps
Chess Games by ECO Code - More than one million games in PGN format.

Free chess software

See Free chess software

Arasan Chess - Arasan is a chess program for Windows and Linux. It is copyrighted, but allows free distribution, with some restrictions.
Bookup 2000 Express - Bookup is a chess database program for Windows. It is copyrighted. It has a trial period with features that allow the user to edit chess openings, but after that it works forever to display openings and create new ones from PGN files.
Brutal Chess - An open source 3D chess game using OpenGL inspired by Battle Chess.
Championship Chess - Free, including online play, with some limitations on use.
ChessBase Light - Older version of Chessbase, which allows to view games in CBH and PGN format.
CompWebChess - Open source application, which allows to start own chess server.
GNU chess - One of the oldest computer chess programs for Unix-based computers from the Free Software Foundation and has been ported to several other platforms (now default on Mac OS X).
Some Chess - An open source online multiplayer chess program using PHP and MySQL (no java or javascript).
GE Chess: A Google Earth multiplayer 3D Interactive Chess Game
Chess Assistant Light - A database program which reads the Chess Assistant and PGN formats. It can also be used to connect to ICC (Internet Chess Club).