Alternative iPod Firmware - Rockbox
In its current state, the Rockbox interface is utilitarian, graphically sparse, and reminiscent of a command-line system, and it lacks the flash of modern commercial MP3 players. But where it comes up short in pizzazz, it more than compensates in options and settings, many of which would make the default iPod jealous.
The software remains a work in progress with the official release not due until November, according to the article. The additional features include OGG and FLAC support, gapless playback, crossfades, photo playback, games, and custom themes.
Users will sacrifice some ease of use as well as iTunes Music Store (Protected AAC) compatibility. Currently supported iPods include the 4th Generation iPod (Monochrome and Color), 5th Generation iPod, Nano and 1st/2nd generation Mini.