DeSmuME is the most seasoned open source Nintendo DS emulator. It sports tools designed for hackers, speedrunners, youtubers, and casual gamers. Homebrew programs are supported and can even be debugged through GDB.
The Windows and OSX versions are both relatively feature rich, and there is a small universe of forks and mods that add even more features for casual gaming.
DeSmuME is the origin of RetroArch and OpenEmu Nintendo DS support and is used by several mobile Nintendo DS emulators, with the notable exception of DraStic.
DeSmuME's source code is now hosted at https://github.com/TASVideos/desmume/
Played a few games on this emulator like Phoenix wright and they work perfectly.
An awesome program that I recommend to everyone who wants to run Nintendo DS.
By far the best Emulator for DS games out there. DeSmuME overcomes any buggy issues that other emulators have which include even starting and running a DS ROM. DeSmuME development is such that you do not require any such extra effort to overcome obstacles such as ROM loading issues, Saving games going corrupt issues and other things. So far, I have been able to run DeSmuME smoothly to play a variety of games. The new versions of DeSmuME offer better game performances compared to the old ones. Some Action Replay codes may not seem to work in the new release, but what the heck? The games run Flawlessly. Thank you developers for such an amazing emulator.