DesMuMe

From the DeSmuME FAQ:

DeSmuME is a Nintendo DS emulator and the name is a play of words - DS Emu + ME.

If you're looking for the newest Nintendo DS emulator for Mac, you've come to the right place! ConsoleEmu.com is your source for the latest builds of DeSmuME for Mac OS X (10.7+). Coming soon!

FAQ (+ documentation): http://wiki.desmume.org/index.php?title=Faq

Downloads Windows Mac OS X Linux Android
Download page nds4droid