Word has come in that the Apple TV has been cleverly hacked (yes, already) to play XviD format videos, according to users from the Something Awful forums.
To achieve this, the hardware hacker dissected the Apple TV, removing the hard drive and then mounting it on a Mac, where the drive pops up as a native HFS volume. (Notably, this proves that the device indeed runs a custom version of Mac OS X.) The user was then able to install Dropbear, an SSH server application, in combination with the video container Perian, and finally, a custom script was written to allow the Apple TV to properly read an XviD format video.
Normally, of course, the device only recognizes MPEG4 and H.264 format videos out of the box. No other formats have been tested as of yet, and this hack unfortunately prevents video synchronization since the it uses reference QuickTime files for the videos to properly play. Perhaps this is just the beginning, though.