I’ve found this site about a year ago, which most people here probably already know about: www.carbonfund.org

It allows you to calculate the amount of carbon you create in a year, advises on carbon reduction, and allows you to choose what projects you want to put your donation toward when you offset through CarbonFund. It also lists partners in the project, which may be a determining factor when you buy your next computer, bike rack, or CD – another way to offset your footprint. Something worth considering.