NOTE: To all of you having file browser reset problems, try force stopping and clearing app data. Don't worry, it will only erase your settings.
I am proud to present DSdroid, the fastest and most compatible NDS emulator for Android, voted by it's users!
Features:
On-screen controls
Sound
Microphone
DeSmuME compatibility
Fullscreen landscape (touch input is buggy)
FPS counter
Open Source (https://github.com/SeannyM/DSdroid)
FREE! (however you can donate to support future development)