There are lots of theories about 911, many of them are probably just conspiracy theories, but in my opinion it is necessary to at least take a look at them, for three reasons:
1) We all know today, that the Bush-regime is totally unreliable.
2) The official story is the story told by the Bush-regime itself.
3) If you look at the official story as a whole, too many circumstances fit each other in a rather unlikely way (a sign that the chain of events are not "natural").
Now there is another theory, based on the role of the media - immediately after the basic event.
See a video about it on: Brasscheck TV
alternative link: http://www.ifilm.com/video/2823171
restored link from Brasscheck: http://www.brasschecktv.com/page/92.html