Have a desire to be "carbon neutral"? Several sites calculate your share of a flight's CO2 emissions and allow you to purchase a dispensation :)
For example, www.offsetters.com says my part of a LAX-HNL roundtrip's CO2 emissions can be offset for $39.60 (Canadian dollars), which is about ... $33.34 USD.
www.atmosfair.de is a more complicated site (Conde Nast Traveler says "It offers a complete exegesis of its emissions calculator's figures and methods, which have been vetted by Germany's Federal Environment Agency") and even allows you to select the type of aircraft.
I'm not sure what those companies do with the conscience-clearing money you send in. So, since I've been supporting Trees for the Future for decades, so I think I'll just continue that :)
