iSquint
iSquint is a free and easy-to-use tool for converting videos into MPEG-4 files that the Apple TV can display. It offers support for a very broad set of video formats, including QuickTime, DV, AVI, XviD, Divx, and Windows Media—among others. With all the codecs and file formats used by various video-capable devices and Internet users, iSquint’s capability to convert the vast majority of files into something that can be played on the Apple TV and iPod make it a must-have tool for any Apple TV owner.
iSquint also offers a very simple drag-and-drop interface. Simply drop your video files into iSquint and it can convert them and add them to your iTunes library with a couple of clicks. Depending on the processor in your Mac and the video formats you choose, conversion can take some time. But that is the case with most video conversion tools.