Well, everyone seems to be on Facebook these days. And sustainability pledges are gaining ground on sites like The Nag and the Guardian's Tread Lightly. So it was inevitable that the twain would meet... which they have, in a just-debuted Facebook app called MakeMeSustainable.
Not content to tell the world about sustainability, this app analyzes your carbon footprint, then gives you concrete ways to reduce it, by pledging to switch to fluorescent bulbs or a reusable water bottle. And a "carbon tree" shows how much you and your friends have reduced your footprint. Of course, unless these guys have a spy network I haven't heard about, they won't be checking your house to make sure you installed that low-flow shower head you pledged to buy last April. But for Facebook addicts thinking about their New Year's resolutions, here's a good place to start.