Rainforest Action Network
   Works to protect the Earth's rainforests and support the rights of their inhabitants through education, grassroots organizing, and non-violent direct action.
   http://www.ran.org/

The Ruckus Society
   Tree climbing, banner hanging and all manner of Direct Action Training. Committed to making other environmental activists and their campaigns more effective.
   http://www.ruckus.org/

Times-Up!
   Environmental group in New York City with accent on bicycling and pedestrian rights and activities.
   http://www.times-up.org/