Alternative browsing, alternatives to accessing Wikipedia through your web browser (mobile devices, desktop integration, alternate portals, etc.)
WatchlistBot is a bot that delivers realtime alerts via instant message (XMPP) when watched articles are edited or when watched users or IP networks edit.
Navigation shortcuts offer the ability to add personal links to the sidebar, providing quick and easy access to favourite articles within Wikipedia.
Finding duplicated references: a tool that will find references with the same URL on a page, with some false positives and missed items, is the URL Extractor For Web Pages and Text. It is not a Wikipedia tool, and there may be other tools available for the purpose. Instructions on its use for Wikipedia are in WP:DUPREF. Such references can often usefully be merged, using <ref name= xxx/> for all except one.
Wikipedia:Wiki2VCS, script that loads histories onto one's computer, so that they can be quickly diffed and searched
XTools Page History Page statistics and visualization, provides sortable and exportable list of all contributors with number of edits and amount of added text. Provides also results of syntax and grammar checks and latest assessment history.
Finding the responsible user
WikiBlame, searches for given text in versions of article
whoCOLOR, browser script for Grease/Tampermonkey, highlights original authors directly in the article, gets data from a publicly accessible API
Editor Interaction Analyzer compares the edits of two to three specified editors to see which articles overlap, sorted by minimum time between edits by both users. Only works on the English Wikipedia. Speed: slow.
Intersect Contribs, compares the edits of two to eight editors at any WMF wiki to see which articles overlap. Speed: fast.
Intertwined contributions, merges the contributions of two editors at any WMF wiki into a single list. Speed: fast. (Currently not working: error connecting to database.)
MediaWiki Table Utility or this updated version This class constructs a MediaWiki-format table from an Excel/GoogleDoc copy&paste. It provides a variety of methods to modify the style. It defaults to a Wikipedia styling with first column header.
csv2other: a free open source tool, in .net, to convert CSV and EXCEL files to wiki table format
LibreOffice Writer is free. It can open almost any file format. It can export to Mediawiki: File menu > export > save as type > MediaWiki. It will save the file as a .txt file which can be opened with any text editor. Copy the wiki code from the text file. You can save any web page as an HTML file, and then open it in LibreOffice Writer. Edit as needed. Remove the parts you don't want. Keep only tables for example. Then export to MediaWiki. Tables can be further edited in LibreOffice Calc. See: Commons:Convert tables and charts to wiki code or image files. And: Help:Table and the section on spreadsheets and the Visual Editor.
Html2Wiki is an extension for MediaWiki that imports HTML