I was passed a link on ICQ to a bunch of shots showing SuSE Linux being ran on an Xbox console along with a nice fluffy penguin toy on top of the system. The page also has a few videos showing the feat. I don't know why you would really bother though, the Xbox was made to be used to play games with mates around a couch with beers in hand, if you ask me - but that's just my opinion.

More information at Xbox Linux Project