I'm all for government conspiracies, but one that keeps popping up on just about every site, from Conspiracy Planet to Above Top Secret, has really been bugging me. According to them and many others, a plane didn't actually hit the Pentagon on September 11, 2001 - instead, a van was sent next to it carrying explosives, or some such nonsense. As with the most ridiculous and easily discredited conspiracy theories, this was one was clearly formulated by someone who knows next to nothing about planes, collisions, physics, or basic science. Instead, the writers have looked at some pictures from the crash and made a layman's observation, similar to all those nuts who claim we never actually went to the moon.
Like I say, I'm absolutely not against far out conspiracy theories - I just hate when those who forward them ignore all evidence to the contrary, or make no attempt to contact qualified experts to answer their questions. So before you go around saying that the Pentagon didn't get hit by a plane, do a service to yourself (and the honor of all those who died on that plane) and read the following (hell, if you still believe we didn't go to the moon, read the other link).
-Snopes: Hunt the Boeing!
-Bad Astronomy: Yes, We Really Did Go To The Moon!