I'm trying to crop the sides of a movie which are unwanted... Online
BEFORE I would say
onetruemedia.com 

It HAD a great online video editor, but that was bought out by disney and then shut down. (Disney just wanted the tools in one of their software bundles)

Currently I would say 
videotoolbox.com
Not the most intuitive, actually a very poor user interface.
But it has the crop feature you are looking for, not easy to find.
But here is a little video on how to use the online tool