RetroArch - RetroArch is a frontend for emulators, game engines and media players.
DeSmuME - DeSmuME is a freeware emulator for the NDS roms & Nintendo DS Lite games created by YopYop156.
melonDS - A Nintendo DS emulator with support for commercial games.
Drastic - Drastic is a Android DS Emulator
VisualBoyAdvance - VisualBoyAdvance (VBA) is a free software (GNU GPL) emulator targeted for the Game Boy, Super Game...
No$GBA - If you have no money you can play Nintendo DS and Gameboy Advance game.