I highly recommend watching 9/11:Press For Truth. While you may or not agree with the conclusions, no one in the media bothered to connect the dots. There are many dots there and they are not conspiracy theories. I watched this a year ago and then recently in light of all the stories coming out of Pakistan and wondering why they are our ally.
While we may never know the motives of the CIA, it is quite certain that many people knew about 9/11 before it happened. In the years after 2001, whenever someone spoke out with the truth, they were quickly vilified by the administration, pundits and the news media. In a true democracy, the media would have jumped on these stories to test their veracity but they didn't. The media covered Clintons's BJ more than investigating 9/11. The US spent more money and more time investigating the BJ than they did investigating what happened on 9/11 and why. You can watch it on google video, if you'd like. Netflix also has it. Perhaps you'd like to host a screening.
I would also recommend No End In Sight if you would like to know who is to blame for the clusterfuck in Iraq. It was hard for me to watch this flick without getting furious and I'm a pretty mellow person generally (really.) But when I even think about what I learned from No End in Sight, I can feel my heart beating.
Controversial documentaries I've watched:
I found Zeigeist the Movie interesting. It asks, "What does Christianity, 911 and The Federal Reserve have in common?" I haven't made up mind on it but it does contain a lot of information worth investigating. It's online here.
9/11 Loose Change. May not answer your questions. May be too far out there for some, but it raises a lot of questions that you too may have been thinking about. It's online here.