Well it took three years, but Rockbox 3.0 has finally made it on the scene, with a major overhaul in the sound decoding department and support for several new players. This open source firmware replacement is chock full of tasty new features, including codec support for over 15 formats like FLAC and Ogg, 5-band parametric EQ, MPEG video, multilingual interface, Doom and a pile of other games, not to mention freedom from iTunes. Oh yeah, and it can talk to you via a spoken interface -- which comes in handy for not driving off bridges and what not. iPod, iriver, Sansa, iAudio, Gigabeat and Archos models are all supported, though Archos didn't get many of the major 3.0 improvements like expanded codecs.
[Via Ostatic; thanks Eric L]