RockBox is custom firmware that runs on many portable music players, including (older) iPod, Archos, SanDisk, iriver, and quite a few others.
i installed it last night on my old fifth-gen iPod Video. installing it was just like installing a program. i plugged in my ipod, ran the app, and waited for it to finish. it let me choose a theme during the install - most are ugly, but i found one that appealed to me.
Rockbox Themes - rayboradio_OB Theme
booting into the new firmware reveals a completely unfamiliar interface. music is accessed either by browsing the filesystem, or by building a database from tags. no software is required to add music to the iPod with RockBox on it. just drag and drop wherever. i keep my music organized, so i don't bother with the database.
now here's the real treat - my ipod now plays
flac, and it sounds absolutely phenomenal! RockBox gives me much greater EQ control. i can roll the bass all the way up without any distortion. it drives my headphones (mid-range Sennheiser earbuds) much better than the old iPod firmware. music is stronger, crisper, and more dimensional than ever before.
RockBox also allows for cross-fading, replay gain, and lots of other nice musical things.
it also comes packed with crap like apps and games - you can even play Doom on the thing - but i really don't care much about that sort of thing.
i've been upgrading my collection to flac, and RockBox is a lifesaver. no more converting/syncing with foobar to add/remove music. just plug it in, drag it over, and it's good to go.
oh yeah i almost forgot - it's 100% open source
check it out!
Rockbox - Open Source Jukebox Firmware