In this op-ed piece, Gregg Easterbrook starts off by critically mentioning Al Gore’s prodigious home energy use, then goes on to explain how the carbon offsets Al buys work in the real world to sequester carbon. Basically, he buys an offset from a company that uses that money to cover methane producing landfills. Since methane is ten times as strong a greenhouse gas as carbon, this is a leveraged use of the money.
He then goes on to explain his reasoning for opening up world markets in carbon offsets, primarily because of China’s skyrocketing carbon economy. If you’ve had a hard time getting your arms around the offset concept, this may help.

Update: Franke James offers this in a comment (below) but I thought it was so relevant that I’m including a link: The Carbon Neutral Myth (warning- 80 page pdf download)
Thanks Franke!