Sustainable Travel International is just one of 35,000+ groups listed by members at iGive. Here's a little more detail on them, as provided by members or the organization itself:
Sustainable Travel International (STI) is a membership-based, 501(c)(3) non-profit organization whose mission is to promote sustainable development and eco-friendly travel by providing programs that help travelers and
travel-related companies protect the environmental, socio-cultural and economic needs of the places they visit, and the planet at large. For more information, please visit www.sustainabletravel.com.