See also State of Linux audio players
Here is a comparison of few free video editors available. They are tested on Ubuntu.
Kdenlive (tested march 2014)Current winner. Does all I need without issues. UI could use some polishing, but good enough.
OpenShot (tested summer 2013)
Decent video player. Crashes randomly but is still usable. Ui misses some features, such as moving a clip to end of previous clip which makes editing long videos painful. Also there's still no way to select multiple clips.
PiTiVi 0.15 (tested jan 2012)
Mediocre but not bad UI. Preview becomes so slow that it's practically a slideshow with multiple 720p videos. Crashes frequently. Development is active but work is done for next version based on gstreamer editing services. I had a problem with rendered files having zero size, but this was fixed by removing gaps from the project. Many thanks to thiblahute on #pitivi.
Cinelerra (tested spring 2011)Crashes so often that it's useless. UI looks like it's from 90's.
VLMC (checked summer 2013)
Spawned from VLC media player. Looks promising but i suppose develoment is dead as the official repository doesn't have packages for current or previous Ubuntu release.