I think I saw something about an XBMC experimental project for the 360 in the usual places. I don't own a 360, so I don't know much about it.
In any case, if anybody is looking to get rid of an unmodded 1.0 or 1.1 XBox, let me know. I recently ripped a trace out of my xbox (the d0 trace, so it wont boot at all), and I'm not willing to buy a new mod chip or do any more soldering.