I'm not sure what the human fascination with conpiracies is drawn from. After every major historical event now it seems theories sprout up about what really happened or what our government isn't telling us. Was JFK shot by the grassy knoll? Were the Kinghts Templar involved in Richie Cunningham's career? Is Paul dead and replaced by a robot? Is his memory full?
Perhaps it comes from history class. I remember the point being outlined many times in my Connecticut liberal public school education that history is written by the victors. That even commonly held accounts of the Revolutionary War, the Civil War or Vietnam are heavily skewed towards promoting US supremacy. I was a child at the peak of the Cold War, and it often seemed every movie was about Russia succombing to the capitalist wise-cracking might of America. Looking back now, I wonder if what we had was so much better than the Russians or if that's what we were supposed to believe.
My current obessesion/timewasting activity is to read about the myriad 9/11 conspiracy theories. It's undeniable that the destruction of the WTC was a polarizing event which conveniently divided the world into Us vs. Them. The benefits to the current White House administration were many (despite how it has blown up in their face.) It's not a very far leap of logic to consider that Cheney and Co. (Coming from Disney Films this Christmas!) perpetrated the attacks or were at least complicit. I've watched enough Jack Bauer to know that this shit happens all the time.
This is a exhaustive list of current 9/11 theories. The wiki editors do a good job of keeping this article neutral, neither endorsing or dismissing the claims. It's a decent read, even if you don't believe a bleeding word of it. I'm not sure where my own opinion lies, but some of the evidence presented (including corroborating eyewitness testimony of explosions in teh WTC basement as the planes crashed into the top of the tower) are too compelling to deny outright.
Another new conspiracy (for me) is outlined here. This is well-thought out and comprehensive thesis proving that Jesus did not exist. Historically. That there is very little evidence to support the claims that he was a social activist or even a public speaker. Instead, this dude proves that the gospels and the subsequent new testament were mythic writings on par with Homeric literature. Interesting, if you can deal with the wall of text on that page.
Finally, the pyramids were made by aliens because Egyptians are stupid.