Mini vMac - The Mini vMac emulator collection allows modern computers to run software made for early Macintosh...
jGameBase - jGameBase is a fully-featured retro-gaming emulator frontend and game database utility.
Basilisk II - Basilisk II is an Open Source 68k Macintosh emulator.
Z26 - Z26 is one of the best emulators for the Atari 2600.
Steem Engine - Steem is an open source Atari STE emulator for Windows and Linux.
Javatari - Javatari is a multiplayer Atari 2600 emulator written in pure Java with no external libs.