Kega Fusion - Kega Fusion is an emulator for the Sega Genesis / Megadrive, Master System, Game Gear, 32x...
Mesen - Mesen is a NES/Famicom emulator and NSF player.
Gens - Gens is a Win9x based emulator for the SEGA Genesis/Mega-Drive/Sega-CD/
Nestopia - A portable and cycle-accurate NES emulator written in C++
RetroArch - RetroArch is a frontend for emulators, game engines and media players.
FCEUX - FCEUX is a Nintendo Entertainment System (NES), Famicom, and Famicom Disk System (FDS) emulator.