Bruce Schneier:

How to fly, even if you are on the no-fly list: Buy a ticket in some innocent person's name. At home, before your flight, check in online and print out your boarding pass. Then, save that web page as a PDF and use Adobe Acrobat to change the name on the boarding pass to your own. Print it again. At the airport, use the fake boarding pass and your valid ID to get through security. At the gate, use the real boarding pass in the fake name to board your flight.