Wired 13.07: START
Only a few months old, with a staff just out of grad school and a membership of fewer than 1,000, TerraPass is no match for the world’s half a billion cars – the second-biggest source of greenhouse gases. But Ned Ford, a member of the Sierra Club’s Global Warming and Energy Committee, believes TerraPass could change the way people think about energy and the environment. ‘Politicians and business leaders have been telling us for the last 20 years that there’s this huge painful cost associated with reducing carbon,’ he says.
‘If you think about your own personal impact on CO2, and you find out you can offset it for a reasonable amount of money, it makes you think differently about the problem. TerraPass is mind opening,’ he says, ‘and that’s pretty cool.’

This is from last year, but still valid. I use TerraPass for my Prius and we plan on using them to carbon-neutralize our tour busses this year as well.