Center for Biological Diversity. Works to combat threats to endangered species and climate change. Includes an extensive collection of research papers.
Greenpeace. International NGO with a goal to "ensure the ability of the Earth to nurture life in all its diversity."
Earth Island Institute. Acts as an environmental umbrella organization working to help people and groups develop environmental initiatives.
Earth Justice. Environmental interest organization headquartered in San Francisco dedicated to litigating environmental issues.
Environmental Defense Fund. Works on global warming, ecosystem restoration, oceans, and human health. See their list of reports and publications.
Fauna and Flora International. Works to conserve threatened species and ecosystems worldwide.
Nature Friends International. Global environmental organization working in environmentally sustainable tourism and cultural and natural heritage.
International Union for Conservation of Nature. Union of governments and civil society organizations working to enable economic development and conservation to take place together.
National Wildlife Federation. Wildlife conservation group also active in the areas clean energy and climate change, with research reports going back to 1998.
Nature Conservancy. Conservation organization working to protect ecologically important lands and waters for nature and people.
Natural Resources Defense Council. International environmental advocacy group composed of lawyers, scientists and policy experts.
Wetlands International. Global not-for-profit organization dedicated to the conservation and restoration of wetlands.
World Agroforestry Centre. Provides knowledge about the benefits of agroforestry for improved livelihoods and environmental benefits.
World Resources Institute. Conducts research in the domains of climate, energy, food water, forests, equity and more.
World Wildlife Fund. International Conservation Organization working in countries around the globe.