Here's some I managed to find though my knowlege on most of these is limited... Feel free to post anything I might have missed!
AmEDS-Amstrad CPC 464 and Amstrad CPC 6128
CrocoDS-Amstrad CPC 6128
DSMasterPlus-Sega Master System
DSNES-SNES
FrodoDS-Commodore 64
GNUboyDS-Game Boy and Game Boy Color
JEnesisDS-Sega Genesis/Megadrive
Lameboy-Game Boy and Game Boy Color
NestorDS-NES
NES DS-NES
PicoDriveDS-Genesis
SNES DS-SNES
SNEmulDS-SNES
SnezziDS-SNES
StyxDS-Atari ST
ThomDS-Thomson Mo5
DS81-Sinclair ZX81
DSpec-ZX Spectrum
dualSwan-WonderSwan
MiniVMac-Macintosh Plus
SpeccyDS-Sinclair ZX Spectrum
Dreamcast VMU-VirtuaMunstazDS
AmEDS-Amstrad CPC 464 and Amstrad CPC 6128
CrocoDS-Amstrad CPC 6128
DSMasterPlus-Sega Master System
DSNES-SNES
FrodoDS-Commodore 64
GNUboyDS-Game Boy and Game Boy Color
JEnesisDS-Sega Genesis/Megadrive
Lameboy-Game Boy and Game Boy Color
NestorDS-NES
NES DS-NES
PicoDriveDS-Genesis
SNES DS-SNES
SNEmulDS-SNES
SnezziDS-SNES
StyxDS-Atari ST
ThomDS-Thomson Mo5
DS81-Sinclair ZX81
DSpec-ZX Spectrum
dualSwan-WonderSwan
MiniVMac-Macintosh Plus
SpeccyDS-Sinclair ZX Spectrum
Dreamcast VMU-VirtuaMunstazDS