Open Source for Mac OS X

First, the bare-metal description. Kdenlive is a non-linear video editor for Linux, FreeBSD, and OSX. It supports realtime input from camcorders (DV, HDV, professional, etc), cameras capable of MPEG4 and H264 output, and standard USB-compliant webcams (some of them, that is). File I/O is supported for a variety of video and audio codes and formats, including AVI, MPEG, FLV, raw DV, WAV, and many others. Kdenlive's editing features include a track-based A/V mixer, effects and transitions processing, keyboard accelerators, and non-blocking rendering. Of course all common editing operations are also supported, e.g. cut/copy/paste, splicing, track solo/mute, and so forth.