Wouldn't it have been nice if you could've participated in the blogging hype about Snakes on a Plane while actually on a plane? Should another opportunity like that arise, you'll be able to jump on the bandwagon thanks to The Definitive Guide to Airline and WiFi and Internet Access, which lists the airlines and flights on which you can get online (for varying values of “online”).
The list isn't as useful as one might hope. There are only two brands of online access offered by airlines: Connexion By Boeing, which will be discontinued at the end of 2006 and OnAir, which currently offers a limited subset of services and typically works through the seat-back video screen rather than your own laptop.