What's Your Green Celebrity IQ??

Kristin Davis got her hands on the wheel of the limited release Hydrogen 7. The car, which has an internal combustion engine rather than a fuel-celled powered one, can run on either hydrogen or gasoline, has a 260-horsepower, and a 12-cyclinder engine, but does zero to 62 in 9.5 seconds (which isn't much speedier than the 4-cyclinder Prius).

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The BMW Hydrogen 7: Paving the Way into the Future

SJP's massive salary (once reported at $38 million per year) is just one perk of the job—there's also the endless supply of designer freebies. Luckily for some NYC gals, this fashion vixen spring cleans her closet frequently, and drops off bags full of brand-new, unworn clothes, from Marc Jacob purses to Fred Segal jeans at consignment shop Ina.

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Thrift Stores Become Eco-Hip Mecca for College Students

The duo's goal is to demand a safer vaccine supply and schedule for children. "This day will go down in history as a time when parents' voices and their message to change the vaccine program was finally heard and acted upon," says MccCarthy, who volunteers with Green Our Vaccines.

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Hollywood Green Episode: Jenny McCarthy's New Book

Strings from Mayer's guitar are donated to the Wear Your Music Project, which makes bracelets from them then donates proceeds to charity. Cameron Diaz and Lindsay Lohan are proud owners of guitar string bracelets.

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John Mayor is a "Groovy Tree-Hugger"

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Brad Pitt's Green Wash, Gwyneth Paltrow's Fur Controversy, Miley Cyrus's Eco-Message and More
Gwyneth Paltrow's Eco-Smart Life

Isabella Rossellini knows her bug sex. The Italian model and film star wrote, directed, and starred in "Green Porno," a series of films detailing the sex lives of various bugs, arachnids, and molluscs. They originally debuted at the Sundance Film Festival earlier this year and are available online on the Sundance Channel.

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Watch "Green Porno," Isabella Rossellini's Nod to Sex, Online

Go-to green gal Natalie Portman added her eco-sensibility to Project Runway. Each of the contestants had to make a dress out of 'environmentally responsible' materials, such as hemp and organic silks. Portman knows a thing or two about fashion--besides her red carpet outings, she also once designed a line of vegan shoes, called Te Cesan.

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Johnny Depp's Green Home, Dark Knight's Eco-blunders, Natalie Portman's Green Project Runway, and More Vintage Video: Natalie Portman's Early Green Days

Johnny Depp is going public with his eco-lifestyle. A few years back, the super-private actor and hater of Hollywood excess bought a 35-acre Caribbean Island he endearingly named "F*ck Off Island." Now he's planning to have his "leave me alone" paradise run on clean energy.

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Johnny Depp's Green Home, Dark Knight's Eco-blunders, Natalie Portman's Green Project Runway, and More
Host an Oscar-Night Dinner, Johnny Depp style

The Cheetah Girls, Katharine McPhee, Jordin Sparks, and other attendees also signed the car's hood, to be auctioned off by Jetta to benefit the City of Hope, California's renowned cancer treatment center.

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Paris Hilton for President? Plus: Ben Harper Takes a Ride, Maggie Gyllenhall Protects the Climate, Amanda Beard Bares All, and More
SustainStyle: Gossip Girl, Design For Humanity, In The Sheets + More

Gyllenhall watched democracy in action when she judges the contest, which prompted U.S. citizens to do more than just rock the vote by submitting videos that challenge presidential candidates to take action against climate change.

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Paris Hilton for President? Plus: Ben Harper Takes a Ride, Maggie Gyllenhall Protects the Climate, Amanda Beard Bares All, and More
Green Geeks Get Tech Oscar