DeSmuME - DeSmuME is a freeware emulator for the NDS roms & Nintendo DS Lite games created by YopYop156.
RetroArch - RetroArch is a frontend for emulators, game engines and media players.
VisualBoyAdvance - VisualBoyAdvance (VBA) is a free software (GNU GPL) emulator targeted for the Game Boy, Super Game...
Mesen - Mesen is a NES/Famicom emulator and NSF player.
Snes9x - Snes9x is a portable, Super Nintendo Entertainment System (SNES) emulator.
mGBA - mGBA is an open source emulator of the Game Boy Advance. The goals are speed and accuracy.