Cinelerra is an audo and video compositing program much like Broadcast 2000 was before it was pulled due to nastygrams from lawyers. From the description:
If you want to make movies, you want the compositing and editing that the big boys use, you want the efficiency of an embedded UNIX operating system combined with the power of a general purpose PC, or you just want to defy the establishment, the time has come to download Cinelerra.
Also of note are pointers to simpler video editing apps:
Cinelerra is not for consumer use. If ease of use, simplicity, and convenience are your thing, you should use Virtualdub, Kino, MJPEG tools or MainActor instead.
There is also linkage to the sourceforge project page.