I just finished watching a 2 hour special on The History Channel, which with the help of Popular Mechanics, debunks the most "popular" conspiracy theories about the events on Sept. 11. They take a look at the mainstream conspiracy theories, many based upon the propaganda piece "loose change", and debunk them with facts, something they show the conspiracy theorists, or as they call themselves "truthers" fail to do.
Some of the most popular conspiracy theories are about the collapse of Building 7, the plane that hit the Pentagon, and the theories that it was an "inside job" are all well explained and debunked. They have been showing this several times this weekend and the site lists the upcoming times. It's a great special and I recommend everyone to take the time to watch it.