This is by far one of my favourite 9/11 conspiracy theories...that of Delmart Edward Joseph Michael Vreeland II...
Mike Vreeland was sitting in a Toronto jail, having been arrested on fraud and other charges, by the RCMP and was awaiting trial. On August 11 and 12, Vreeland demanded that he be put in contact with national security officials from both Canada and the US. He claimed that he was an officer in the Office of Naval Intelligence, and that he had information vital to the national security of both countries. His demands were denied, so on August 12, 2001, he scribbled a note and sealed it in an envelope, and gave it to his jailers. Three days after 9/11, the envelope was opened, and on the paper were written the words "World Trade Center", "Pentagon", "Whitehouse", "Parliament Building", "Sears Tower" and the 'Royal Bank Building in Toronto" as well as the name "Bin Laden". Also written at the bottom of the page was the phrase "Let one happen. Stop the rest".
The US government denied that he was of the Office of Naval Intelligence, and claimed that he was discharged in 1986 after two years, for dissatisfactory service. However, during a court appearance, while the prosecution were trying to portray him as a fraudulent con-man, his defense lawyers brought a speaker phone into the court room, and called the Pentagon. The operator confirmed that Mike Vreeland had an office at the Pentagon, and held the rank of Lieutenant, and even provided his direct phone number.
To this day, many people consider Mike Vreeland to be a clever con-man who manipulated people to get what he wanted...however, the RCMP have it on record that he wrote the note with the potential terrorist targets, and that it was sealed in an envelope for a month before the attacks...
http://propagandamatrix.com/multimedia_priorknowledge_vreeland1.html
http://members.freespeech.org/ltvreeland/interviews/rupport040402.html