Burlington, VT
Ithaca, NY
Corvallis, OR
Springfield, MA
Wenatchee, WA
Charlottesville, VA
Boulder, CO
Madison, WI
Binghamton, NY
Champaign-Urbana, IL
Ann Arbor, MI
San Diego, CA
La Crosse, WI
Pittsfield, MA
Eau Claire, WI
Durham, NC
Norwich-New London, CT
Eugene, OR
San Francisco, CA
Chico, CA
Harrisburg-Carlisle, PA
Barnstable Town, MA
Utica-Rome, NY
Missoula, MT
Asheville, NC
I would say that Greensburg, KS should be mentioned here too. If you do not have the Planet Green channel which airs Greensburg , check out Greensburg's website.
Though not in the US, I will put a note in here about a village in the United Kingdom, Ashton Hayes, that is striving to be the first village in the UK to go carbon neutral.
I hope this list grows exponentially larger every year as people become increasingly concerned with their impact on the planet.
