It didn't take long for our jailbroken AppleTV's to get rocking with custom Apps. The first app to come to AppleTV is called nitoTV.
nitoTV is a front end application for the popular mplayer media player. Using perian and Apple's DVDPlayback.framework, users can create playlists and add files or folders of their choice.
So what else does NitoTV do? Well it's more than just a media player. Supposedly you can even use NitoTV to play nes, snes, genesis, game gear and gameboy advanced roms, view RSS feeds and 3-day Weather forecasts.
At this point, you should be able to play almost any media file type. However, the installation process might have the unexperienced scratching their head. You will be required to SSH the files over to your AppleTV.
Note: The current installer packages are NOT for AppleTV 2, but the original AppleTV.