By the way, people are staring themselves blind on the physical evidence. The whole JFK assassination thing proved that that's not enough to put something in the spotlight. For someone looking for more
non-concrete information regarding a (possible) 911 conspiracy, this is a good starting point:
The coincidence theorist's guide to 9/11.
I can also recommend Mike Ruppert's book, Crossing the Rubicon, if you're not put off by reading 500 pages about air force drills, shady monetary transactions and the inner workings of intelligence agencies.