Rockbox is an open source replacement firmware for mp3 players. It runs on a number of different models:
* Archos: Jukebox 5000, 6000, Studio, Recorder, FM Recorder, Recorder V2 and Ondio
* iRiver: H100 and H300 series
* Apple: iPod 4G (grayscale and color), 5G (Video) and Nano
* Additional models are in development
Rockbox is a complete rewrite and uses no fragments of any original firmwares.