When GURU talks about “clean energy,” we mean it (”dirty minds,” too, but that’s for another time). And not just the kind you find in a certain organic energy drink. We told you about Bixi back in May, now we’re on board with the Zipcar. As much as we (and most gung-ho cyclists) would like to believe a bike can take you anywhere, some trips need four wheels: heading out to Ikea, spending a weekend in the country, taking your turn with your office car pool.

That’s where Zipcar comes in. “The car for people who don’t want one” is how they put it. By signing up through their site, you get hourly or daily access to cars across the United States, in Vancouver and Toronto in Canada, and all the way in London, England. No huge car payments, no monthly parking bill – even gas and insurance are included.

As with Bixi, you get a special card that allows you to unlock and lock your vehicle. And like Bixi, you’re doing more than saving money and getting around, you’re helping out the environment (but there’s no need to be smug about it!).

Zipcar’s so committed to eco-friendliness they encouraged people from 13 Zipcar-zealous cities to go on a Low-Car Diet by swapping their car keys for running shoes, bikes and rollerblades. You can check out their photos, videos and testimonials here.

The results of last year’s challenge?

Now if only some us more coddled urbanites would get around to actually earning our driver’s licenses, we’d be set…

(photos c/o zipcar.com)