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With around 1.2 million members, the Natural Resource Defense Council (NRDC) is one of the nation's largest environmental advocacy groups. Their mission statement, according to the NRDC website is working "to safeguard the Earth: its people, its plants and animals and the natural systems on which all life depends." And if their name, or simply the acronym, sounds familiar—it's probably because it is.

The NRDC has had a hand in many of the nation's environmental laws passing, and is often reached for quotes by publications as prominent as the New York Times. Recently, they've been a major influence in developing the bill that would curb emissions and traffic congestion in California.

They're also hard at work looking for solutions combating global warming, finding alternative energy resources, and preserving wildlife across America. They also perform public eco-services like publishing shopper's guides, participate in music festivals, and make videos with Treehugger founder Graham Hill.

Visit the NRDC's online Action Center to find ways that you can participate in helping to achieve their nobly green goals. You can also help by donating to their cause, or signing on as a member.