Datura is a native Mac OS X interface for one of the most famous command line video encoder ffmpeg.
HandBrake
ffmpegX is a Mac OS X graphic user interface designed to easily operate more than 20 powerful Unix open-source video and audio processing tools including ffmpeg the “hyper fast video and audio encoder”, mpeg2enc the open-source mpeg-2 encoder and multiplexer and mencoder the mpeg-4 encoder with subtitles support