Set up an Ubuntu Linux based media center with Mythbuntu
Just as Ubuntu is designed to make Linux accessible to the casual user, Mythbuntu is designed to bring media center software to the masses. Of course, that's what Windows Vista does, but for anyone interested in open source applications, MythTV is the way to go, and Mythbuntu makes installation a relatively painless process.
The current version is a public alpha, so don't expect everything to work perfectly. But if you download the disc image, burn it to a CD, pop it in your computer and reboot, you should load up a MythTV frontend. That's the part that lets you interact with media. If you want a fully functioning media center that can record record television shows, you'll want to install the backend as well. If you've already got a backend machine running, you can access it from the frontend included on the liveCD.
Still, the LiveCD is a great option for anyone who wants to see how MythTV works without having to repartition or reformat their hard drive.