In a survey done by Tufts University and Corporate Knights ("The Company for Clean Capitalism"), Seattle has tied for the #1 Greenest City along with San Francisco and Portland. Researchers looked at the programs and policies in place to promote sustainability.
I'd be surprised if Seattle wasn't #1 on this list! I've never lived anywhere that promoted more recycling, shared transportation and sustainable living practices. Gotta love it!
Here's the full list (scores to the right, out of 38):