Eckart Wintzen is my hero since I worked at his company, Origin, back in the 90s. He actually implemented that concept at Origin: We had to track and estimate the footprint of each project, and then the amount was reinvested in environmental projects.

Recently I have created a methodology inspired by that experience at Origin: http://www.scribd.com/doc/5507536/Sustainable-Software-Engin...

More info about Eckart Wintzen (who passed away recently): http://www.wired.com/wired/archive/4.11/es_wintzen_pr.html