Well the most common conspiracy theory in the middle east appears to be "the Jews did it". Which I heard both in Egypt and from a couple of people of middle eastern background that I and my husband work with in Melbourne. As I understand it, the theory is that there were no Jews killed in the collapse because the Worldwide Conspiracy Leadership told them all to get out before the attacks. Any reports of Jews being killed are therefore false and part of the Worldwide Conspiracy to blame the Arabs for everything. *shrug*

It's not just in the middle east, apparently that one's made the rounds in the US as well.