Are these 9/11 conspiracy theories still around? I thought they had all been debunked.
First, the conspiracy theories leave huge questions unanswered or would require conspiracies on such an unimagineably huge scale as to be impossible. The orignal conspiracy theory is generally attributed to Thierry Meyssan, a super-leftist government-hater, who I believe has said that he doesn't know how the conspiracies could have been pulled off and leaves the "big" questions (how the conspiracy was done, by whom, and for what purpose) unanswered.
Second, the conspiracy theories are based on "problems" with minor details rasied by unqualified theorists: I think the WTC should have not have fallen. There should be more debris. The hole in the Pentagon isn't as big as holes in other buildings hit by aircraft. The exact shade of blue on this piece of wreckage doesn't match the exact shade of blue on this other picture of an American Airlines plane. A witness said the plane "sounded like a missle." And so on.
Third, even these minor details have all been debunked by professionals in the appropriate fields. Even if we simply woke up the day after the attack and had to figure out what had happened, the overwhelming evidence would lead to the conclusion of planes hitting buildings. Any other conclusion could only be supported by evidence of some super-huge impossibly massive cover up.
A good short artical with some interesting links is at http://urbanlegends.about.com/library/blflight77.htm