A few weeks ago, I built an XBMC-based media player to use with the 32″ TV in the living room:

I decided to make another system using an original XBox for the bedroom, since I don’t need to play HD content on the 19″ TV in there. I bought a refurbished XBox from Gamestop for $54 shipped, and picked up the rest of the pieces I needed (XBox-to-USB cables, an 8M memory card) off eBay and from a local shop. I used a 10″ LCD TV while setting it up, so I didn’t have to run back and forth to the bedroom.
Here’s the XBox after doing a “softmod” to install Linux and the UnleashX dashboard:

Here it is with XBMC installed, running the default “PM3″ theme:

And here’s the final setup. Hooked up to the 19″ TV, running the same Confluence theme as the system in the living room, with the XBox DVD Playback kit plugged in so I can use a remote instead of a wired controller.

Am really happy with both systems; the living room unit cost me around $200 total while the bedroom XBox setup cost me $90.