There's an easy way in OS X Lion to convert media from one format to another using preset conversion settings. One method uses Automator and can be launched from the Finder. The other uses terminal and either afconvert or the new avconvert command.
The Automator method is the easiest and requires you to go to Finder, select the video file you want to convert and choose "Encode Selected Video Files" from the context menu. This will launch a dialog box in which you can select your video conversion settings and the destination. You can process one file at a time or multiples files in a batch conversion. Automator also works with audio files and the conversion process is the same as described above for video.
OS X owners comfortable with the command l
