Biological Diversity and Tourism International Guidelines for Sustainable Tourism – guidelines from the Workshop on Biological Diversity and Tourism.
Leave No Trace – guidelines for sustainable outdoor recreation, training courses, teaching resources, programs, research.
National Geographic Sustainable Tourism Resource Center – information and links for travel professionals, travelers, and residents, aimed towards promoting environmentally and culturally friendly tourism.
responsibletravel.com – “Holidays that give the world a break” – articles and links to help travelers find environmentally-friendly holidays and accommodations. Volunteering information.
Sustainable Tourism – World Travel & Tourism Council Strategy & Development page.