Sounds like you're looking for Kdenlive:
http://www.kdenlive.org/features
I would also recommend "Ubuntu Studio".
ubuntustudio.org
It is an entire distribution completely dedicated to multimedia production, be it audio, photo, video, and as such it already comes with Kdenlive, and a bunch more useful programs and libraries. I've been toying with the live DVD lately and I'm impressed. For example, with Ardour, I was able to mix a couple of songs from scratch (well, I had the single tracks recorded in advance on another machine) making use of the many free effects that come with it.