RetroArch - RetroArch is a frontend for emulators, game engines and media players.
Gameboy.Live - basic gameboy emulator with terminal "Cloud Gaming" support
mGBA - mGBA is an open source emulator of the Game Boy Advance. The goals are speed and accuracy.
BGB - BGB is a GameBoy and Gameboy Color emulator and debugger for Windows and Wine
DeSmuME - DeSmuME is a freeware emulator for the NDS roms & Nintendo DS Lite games created by YopYop156.
gnuboy - Game Boy handheld game console emulator written in ANSI C