To help atone for their environmental sins, some SUV drivers are turning to groups on the Internet that offer pain-free ways to assuage their guilt while promoting clean energy.

It involves buying something known as a carbon offset: a relatively inexpensive way to stimulate the production of clean electricity. Just go to one of several carbon-offset Web sites, calculate the amount of carbon dioxide produced when you drive, fly or otherwise burn fossil fuels, and then buy an offset that pays for an equivalent amount of clean energy.