While this hack isn’t new, it’s worth revisiting… Life Hacker documents how they upgraded an Xbox into a Xbox Media Center (XBMC). I can tell you from first hand experience that once you have the required supplies (Splinter Cell, USB reader) the process is quick and easy. And when you’ve completed the upgrade, the classic Xbox is more capable, useful, and affordable than most most media extenders out there – including the 360. All sorts of multimedia can be streamed across your home network, played back from the local hard drive, or via the optical drive. Hooks into YouTube and Apple’s movie trailers are included, plus all sorts of other widgets are available.
There’s work going on to port XBMC to Linux… I realize there are fewer classic Xboxes in use these days, but given the highly capable Myth I’m not sure why they’d bother.