Let me first say that until this year, I fully beleived that 9/11 was the work of al-Qaeda and Bin Laden...because I had never bothered to look at any of the conspiracy theories. This year, I finally got curious as to why people were still going on about the attacks being a government job, so I spent a few days looking up videos and reviews. Quite a few of them were sketchy and I was able to dismiss the claims because I could conceive of alternative possibilities to many of the allegations. But a few times I saw things for which I simply could not think of a plausible explanation.
One of the biggest ones was the way WTC building 7 went down. It was indeed hit with flaming debri from buildings 1 and 2, and it was fairly well filled with flames. BUT...it went down uniformly, in 6.5 seconds, like a textbook demolition. Officially, it was the first instance on record of a skyscraper becoming structurally unstable from fire alone (I mean the support collumns and all). Normally, a fire will consume flooring and walls, and the building will fall apart in chunks, but the structural supports will all be left intact. Those are alloyed steel beams, and no building fire is capable of heating those up enough to bring them crashing down. Plus, a slow-mo video of the collapse shows demolition kicker charges blasting horizontally from each floor of the building as it comes down. Technicians also found nanothermite in all of the dust samples from around the buildings. Nanothermite is only used as an explosive - there is no other use for it - and it does get hot enough to eat through support beams. Remember how much time they spent emphasizing that it was the jetfuel that got hot enough to eat the support beams in buildings 1 and 2? Well, what about building 7? No jet fuel there, but it came down the same way.
Another thing was that Bush tripped up in two separate interviews, saying on record that he saw the first plane hit the building on a hallway TV, BEFORE he was told about the incident in the classroom, where he was iconically reading to school children. There were no live news feeds of the first plane hitting, and amateur videos of it were not aired until the next day, so how did he know about it before the dude came into the class and whispered in his ear? Rumsfeld also tripped up in an interview, admitting that flight 93 was shot down. The official Whitehouse story was that the hijackers took the plane down because the civilians onboard had rebeled and were taking the plane back. But it came out later, and Cheney confirms it in a later interview, that the Pentagon ordered it shot out of the sky. If the people were taking the plane back, why shoot it down? Did they know something that the government could not afford to let them reveal by surviving? Perhaps the hijackers were not al-Qaeda, but American G-men, and if there had been survivors they would not have corroborated the Islamist jihad story. That's speculation on my part, but it is not speculation that high-ranking officials contradicted their own official story.
There are quite a few other inconsitencies as well, all of which added up in me to a healthy dose of skepticism in the official story. At this point, I lean toward the idea that 9/11 was a US government-orchestrated "terror" attack with the purpose of catalyzing the adoption of the Homeland Security Act, and now the 2012 version of the NDAA, so that the Bill of Rights could be undermined in broad daylight without anyone making too much of a fuss. But as-per Reading Rainbow, don't take my word for it, take a look for yourself. Below are the videos that clinched it for me, arranged in an order that I think puts the pertinent claims together so that it doesn't all feel jumbled and overwhelming. Some of them overlap a bit in content, and keep in mind, there are going to be a number of claims in some of these videos to which you think 'sure, but that could just as easily have been because...' and I had that same reaction to some of it too, but if you can watch all these and come back telling me that the official story doesn't seem like bullshit to you now, I'll be very suprised.
I know there are a lot of them, but most are only 3-5 minutes long, and a couple are under a minute. The last one is long, and has the best overall analysis, but is still missing some of the points brought up in the ones that precede it. If you're going to bother watching any of them, you may as well watch them all.