iMovie. Go to the share options and instead of picking one of the default presets, choose to do a custom Quicktime export (note, I can't recall the exact terms iMovie uses for this and I don't have it installed at the moment to check what they are). You have a multitude of different file formats and compression settings for each to select from. FWIW, you can still export as a .mov but by using more aggressive compression or lower resolution settings, you can achieve smaller file sizes.