Amiga emulation
Amiga emulation refers to the activity of emulating (mimicking the hardware of) a Commodore Amiga computer system using another computer platform. Most commonly, a user will emulate the Amiga using modern platforms such as Wintel or Macintosh. This allows Amiga users to use their existing software, and in some cases hardware, on modern computers.
A few dedicated Amiga users have taken this even further by writing a hardware Amiga emulator for a common FPGA chips, called Minimig.
One of the most challenging part of emulating the Amiga architecture is the emulation of the custom chipset, which is extremely complex (even though today's graphic processors and digital signal processors outperform it easily) and becomes critical when cycle-exact emulation is required, such as in a few games.
Amiga emulators
At the time of writing there exists no emulator capable of emulating an Amiga with PowerPC accelerator (PPC Amiga). Arguably there is no need for PPC emulation because an emulated Amiga can run 68K software just as fast, if not faster, than what can be achieved through PPC emulation.
Fellow
An actively developed emulator capable of emulating all the common Amiga configurations. (A500, A600, etc...)
UAE
Although the name varies, this emulator exists for Windows, Macintosh, RISC OS, Linux, Unix and other systems, including the Amiga itself. It is capable of emulating an 68K Amiga, including undocumented behavior, with OCS and/or AGA chipsets and modern graphics and audio subsystems, including Picasso96 graphic libraries and Amiga AHI 16 bit audio subsystem.
WinUAE
WinUae has many ports and many different names, however this is THE most popular Amiga Emulator on the Net. With recent releases this can now not only emulate the popular Amiga's (Amiga 500, Amiga 500+, Amiga 600, Amiga 1200 and the Amiga CD32 but now can Emulate the Amiga CDTV system.