Companies/NGO's we enjoy working with and/or would like to recommend to other people:

International
the Gold Standard
Algalita Marine Research Foundation
ImAnAgronomist

Europe
the PAN Parks Foundation

Romania
The Association of Ecotourism in Romania
The Adept Foundation

Pretty interesting sites:
The story of stuff
Kiva

If you would like us to add another related link, you can contact us using our contact form.