List originally created by Heidi Hess from input by Progressive Exchange. Know some other examples or directories? If so, please add them! You can reply to the discussion thread at the bottom of the page, or if you're feeling ambitious feel free to edit the page directly using the EasyEdit button at the top left.

American Cancer Society: http://www.twitter.com/americancancer
NARAL: http://www.twitter.com/naral
Free Press: http://www.twitter.com/freepress
Oxfam America: http://www.twitter.com/oxfamamerica
The One Campaign: http://www.twitter.com/theonecampaign
Amnesty: http://www.twitter.com/amnesty
Sierra Club: http://twitter.com/Sierra_Magazine
Humane Society: http://www.twitter.com/humanesociety
American Red Cross: http://www.twitter.com/redcross
Women's Refugee Commission: http://www.twitter.com/wrcommission
COPEPINK: http://www.twitter.com/codepinkalert
NWLC: http://www.twitter.com/nwlc
Smithsonian: http://www.twitter.com/smithsonian
United Food & Commercial Workers Union, http://www.twitter.com/FCW
Service Employees International Union, http://www.twitter.com/seiu
Food & Water Watch: http://www.twitter.com/foodandwater
Internet Advocacy Roundtable: #iar and http://www.twitter.com/IARoundtable
Feminism 2.0: #fem2 and http://www.twitter.com/Fem2pt0
Transparency Camp 2009: #tcamp09


Individuals
SEIU International President Andy Stern Twitters from his iPhone. Yes, really! http://twitter.com/SEIU_AndyStern
Sierra Club President Carl Pope: http://twitter.com/CarlPope
National Organization for Women President Kim Gandy: http://www.twitter.com/Kim_Gandy