Wikispooks Discounting the Official Narrative as the absurdity it so clearly is, there are just two organisations on the entire planet with the expertise, assets, access and political protection necessary to have both executed 9/11 and effected its cover-up to date (ie the means). Both are Intelligence Agencies - the CIA and the Israeli Mossad whose motives were arguably the most compelling. Those motives dovetailed perfectly with the Neocon PNAC agenda, with it's explicitly stated need for "...a catastrophic and catalyzing event - like a new Pearl Harbor" [1] in order to mobilise US public opinion for already planned wars, the effects of which would be to destroy Israel's enemies.
Agree or disagree but be informed. A word to the wise, there are a lot of "crazies" putting out theories. They are likely red herrings, things for you to chase and find nothing. Just skip over and look for what makes sense to you.