The Economics of Environment and Biodiversity http://www.teebweb.org/
Bank of Natural Capital http://bankofnaturalcapital.com/
Earth Economics Institute http://www.eartheconomics.org/
Forum for the Future http://www.forumforthefuture.org/
New Economics Foundation http://www.neweconomics.org/
World Wildlife Fund International http://wwf.panda.org/
International Union for Conservation of Nature http://www.iucn.org/
Social networking with a purpose: http://www.elpis.com