Mac Mini
The faster of Mac mini models can display video at a maximum resolution of 1080p, compared to the AppleTV's 720p. The Mac mini can also incorporate third-party front-end applications like XBMC Media Center, Plex, and Boxee.
Unlike the Apple TV, the Mac mini is backward compatible with televisions that have only composite or S-Video inputs.
With the release of the March 2009 revision of the Mac mini, the computer now supports the 9400M GPU and Mini Display Port technology to more easily run high resolution media. In fact, the official Apple Service Source manual for Mac mini describes this procedure in detail, even including an official Apple part number for a "modified putty knife".