Adventure Council Big Volcano
Ecotourism Resource Center
Blue Flag
Beaches & Marinas
Business Enterprises for Sustainable Travel
Caribbean Alliance for Sust. Tourism
Ecotourism Society
Ecotravel Center
Conservation Intl.
European Network for Sustainable Tourism
Ethical Traveler
Great Outdoor Recreation Pages
Green Globe
Certification of hotels, etc
Green Hotels Assn
Green Lodging News 
Greenskies
Greentour Foundation
Guardians of the Rain Forest
ICOMOS
I ntl. Congress of Monuments and Sites
Intl. Centre for Ecotourism Research
Inl Inst for Peace Through Tourism
National Geographic Society
Sustainable Tourism Resources
Natl Reg of Historical Places 
USA
Natl Trust for Historic Preservation
USA
Ocean Planet
Smithsonian
Org of World Heritage Sites
Partners In Responsible Tourism
San Francisco Bay Area
The Pacific Asia Travel Association
Planeta
Americas
Rainforest Alliance
Slow Food
Preserving Agricultural Tradition
Sustainable Architecture, Building, Culture
Sustainable Travel International
Tour Operators Initiative
UNESCO
World Heritage Sites
World Heritage Info Network
World Monuments Fund
World Wildlife Fund

Alliance Abroad Group

Assn of Voluntary Service Orgs

Australian Volunteers Intl

Australian Youth Ambassadors for Development

Citizens Development Corps

Conservation Volunteers

Australia 

Earthwatch

GoAbroad

NGO Abroad 

Peace Corps (USA)

The Intl Volunteer Programs Assn 

UNESCO Co-ordinating Com for Intl Voluntary Service

UNWTO.TedQual Volunteer Destinations

Volunteers for Intl Development from Australia

VolunTourism

Voluntourists Without Borders 

WorkingAbroad 

World Volunteer Web