Depending on the codecs used, MPEG Streamclip may be able to do it without re-encoding. Open the MOV, then File>Save As > (Select MP4 from the drop down menu).
Such a beautiful program. I love it. They have a more sophisticated solution called VisualHub if you need more firepower than this -- iSquint is designed for getting videos into iTunes and onto an iPod. But you can do the "TV" video quality or the "iPod" video quality, so you can still get fairly good quality from it. I use iSquint on a weekly basis.