WeMod - Personalize your gaming experience Thousands of free mods and trainers for your favorite single-player PC games — all in one place.
jGameBase - jGameBase is a fully-featured retro-gaming emulator frontend and game database utility.
Cheat Engine - Cheat Engine is an open source memory scanner/hex editor/debugger for Windows.
Z26 - Z26 is one of the best emulators for the Atari 2600.
GameCopyWorld - An index for Game Backup Instructions, No CD Patches, and Game Trainers
Javatari - Javatari is a multiplayer Atari 2600 emulator written in pure Java with no external libs.