I recently watched this documentary, Who Killed the Electric Car and would highly recommend it if you are at all interested in alternative energy. This film is an eye opener to the things that go on behind the scenes. It shows that public knowledge is key and that large conglomerates, whether government or corporate are capable to squashing new technology. I don't even think you could call it a conspiracy theory, this is the real deal.
If you like high gas prices and foreign oil dependancy, don't bother renting this one.
Here's a preview