I'm really big into old video game/computer emulators at the moment. The following links will provide you with some wicked emulators for the Commodore Amiga, Commodore 64, Vic 20, Atari 2600, Colecovision, Vetrex and many many more.

My favourite emulator at the moment is the Multi Arcade Machine Emulator (MAME) which along with links to over 3000 games images can be found at . . .

Arcade At Home

This emulator is constantly under development and continues to support more and more games. Not all games are 100% correct (i.e.. the colours may be wrong, no sound, etc..) but for those old enough to remember the older classic games, it's a trippy blast to the past.
(A Good processor is recommended for maximum emulation enjoyment)

Many other Single Machine and Multiple arcade machine emulators can be found there also. There are also lots of Console emulators (NES, Gameboy etc..) but I don't really get into those as much as the Arcade and Computer emulators.

Check out the NEOGEO, RAINE and CAPCOM Emulators though these are increasingly being swallowed up into Mame.

I am also have my own Mame arcade cabinet under development.
Check it out here (link)