I found this little comparison review of Open Source Video editing programs. The top three came out as KDENLIVE, OpenMovieEditor, and… Blender. Actually, the reviewer claims that those are the only ones he found really usable on Linux. I found it interesting that Blender was on the list, even though it’s primary purpose is 3D animation. Blender does do video editing, and compositing though, which make it a rather well rounded video production package!
And given the fact that it’s the only one of the three that works on both PC and Mac, that helps narrow down the choice for some people! Blender does have it’s drawbacks though, such as it’s steep learning curve, but it’s quite a contender none the less. Of the three negative points that the reviewer pointed out, one is already resolved (Blender now works natively with fractional framerates). I don’t know if it’s going to take the place of Adobe After Effects and Premiere for me, but it’s nice to have another tool at your disposal!