Linux Media Center
I recently downgraded an Apple Powerbook (with busted video/LCD connection) into a glorified media center. It is more powerful than Apple's AppleTV but without the HD support. I attached a bluetooth mouse and keyboard and viola!
If you have an old PC gathering dust in the corner of your home office, why not use it as a media center as well? Here's how you can create an Ubuntu Media Center.
Isn't that great? Who says you cannot use that old PC anymore?