There are emulators out there... most of which are for guys that want to learn how to develope for the DS. and its not too hard to dump the files on the DS cartriges... just have to make a little device to link it to the computer... serveral guys have done it already.
http://www.themodgods.com/
Read stuff on that site/linked from that site ^_^ lots of good info on the DS, including its secret abilities. xD
There are like 3 different emulators I beleive... although one was wrongfully leaked from someone and isn't a finished version.
Each emulator has its things, its not too hard to emulate the graphics of the DS. What is hard to do it get an interface to make the touch screen work, but they've done that.
Mainly, these emulators are for people that want to develope games on the DS. Therefore, homebrew games work best on them.