I found this site which has a nifty carbon calculator that walks you through a bunch of questions and tells you hoe many pounds of CO2 you are responsible for while looking at Participate.net, a pretty cool drupal site by the guys over at Lullabot that aims to connect people with actions/activism through offline activities related to movies (like Syriana and others).
Back to the carbon calculator, by my estimates I am responsible for over 6 tons of CO2 emissions each year because of my air travel.
I recently read about bio jet fuel on WorldChanging.com which first clued me into the huge carbon footprint my air travel contributes too. An average transcontinental flight creates a half ton of CO2 for each passenger!
Guess I better fire up the the bio bus and hit the road!