Avid used to have a free version but they discontinued it (Never did like Avid much even though it's what all the big people use)
Jahshaka's supposed to be good. I've never used it myself:
jahshaka.org - Home
iMovie if you've got a Mac
I've also seen Wax mentioned a few places:
Wax - [ Homepage ]
I actually bought a domain the other day to start some filmmaker forums, but haven't been able to work on it much:
FilmBoards.org • Index page