nds4droid by jeffq is a free, open source Nintendo DS emulator written for Android smartphones. It is based off of the excellent emulator DeSmuME. The source code can be found on sourceforge.

Changes:

* Fixed a bug in the new ROM browser which would cause a crash when a ROM that couldn’t be opened was present on the device
* The new ROM browser now only recursively searches five directories deep on the external storage

http://jeffq.com/blog/nds4droid/