Those following the XBMC (a.k.a. Xbox Media Center, although they'll probably need a name change soon, considering all the platforms they've jumped off to) development for the Mac have some good news coming to them: the release has reached version .1.
It's still as shaky as these things come, but new to this version are fullscreen support, "bleeding edge" ffmpeg libraries, and a regular FPS in video playback. It's still not anything the average user should be running, but as I said, for those interested in following along with the development, it should be welcome news.
The download is available from the wiki, and we're told it's now super simple to install (though actually running stably may be a little tougher) -- just drag into your Applications folder and cross your fingers.
Update: They got that name change: here's the new site.