If you're on a flight with gogo wireless, there are a bunch of promo codes for free internet..
FREEINTERNET should work until the end of the year..
DELTATRYGOGO should work on Delta flights
AATRYGOGO should work on American Airlines flights
Gogo is also running a promotion where you can get a code to give out to people and the person with the most people that use their code gets a few free sessions or something like that.
2287321623nca was the code they gave me; should be good for free in flight wifi until January 7th, 2010
The key for all of these however, is to have them *before* you get on the plane. So if you haven't yet, put them down in your phone or something, just in case you end up on one with service!
I've been doing a lot of flying recently.. nothing better than free wifi on the plane!