The Feroceon CPUs are pretty hefty too. They're powering the Marvell Kirkwood platform which is used in things like the Sheevaplug and some of the QNAP TS-* NAS devices. Debian runs great on those. (2.0ghz CPU, 512mb ram). Probably the biggest trouble here is the lack of an MMU (?) .
One of the SE sites assembled a list. Shockingly, the question isn't closed yet!
http://electronics.stackexchange.com/questions/27594/what-op...