As for free (as in beer) there is no equivalent to Adobe premier (which is not free in both terms), I've heard kino is good, but it is dodgy to compile, hence there is an article on how to proceed
http://www.linuxfocus.org/English/Ju...ticle254.shtml
As for commercial, see what "Lord of the Rings", "Shrek", "Ice Age" others are made of (see the links provided by jostber as well as
http://www.linuxmovies.org/articles.html ), the price of $10K a seat can be concidered a steal when we talk about Hollywood film making.