If you're trying to sort through the various issues raised by reading The 9/11 Commission Report and viewing Loose Change, the resources below may be of some help to you.
New York Times Interactive Feature: Inside the Towers
New York Times Interactive Feature: How the Towers Stood and Fell (heavy on engineering and design)
National Institute of Standards and Technology, Final Report on the Collapses of the World Trade Center Towers
Screw Loose Change (a blog whose title describes its raison d'etre)
