Ok, I have never gotten into the political fracas here, but I will draw the line on this one. The is stuff is right up there with the "4,000 Jews were warned not to go to work" garbage. I have read up on many, many of these conspiracy theories and the arguments against them, and I've weighed the merits of each. The bases of these theories are weak and the links to any substantive causes of 9/11 extremely attenuated at best.
While there are many sources you can find that argue against the conspiracy theories, I think this one is the most concise if you want something general to read. It is an article that gives short, but pointed examination to the major conspiracy theories about 9/11, and no, it's not from a right-winger, oil company, or Fox News. Nor is it from some kid living in mom's basement dreaming shit up - it's from Popular Mechanics Magazine.
The traction that these ideas have gained is a sad monument to the pathetic lack of critical thinking in this nation.