Nestopia - A portable and cycle-accurate NES emulator written in C++
Stella - Stella is a multi-platform Atari 2600 VCS emulator released under the GNU General Public License...
FCEUX - FCEUX is a Nintendo Entertainment System (NES), Famicom, and Famicom Disk System (FDS) emulator.
WinUAE - WinUAE is a Windows port of the emulator UAE.
VirtuaNES - VirtuaNES is Famicom/NES emulator for Win32.
jGameBase - jGameBase is a fully-featured retro-gaming emulator frontend and game database utility.