Surprisingly enough, Blender is actually one of the best free video editors out there. Though you'd probably have to know a bit about Blender's UI conventions first to really get the most out of it. I've tried all the open-source ones out there, but none of them came close to Blender. Though it's worth noting it won't have quite as many bells and whistles as a commercial dedicated program geared towards professionals, but so far it has everything I've ever needed from it and then some.
Here's a pretty good and comprehensive tutorial series for anyone interested:
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