The International Volunteer Programs Association (IVPA) is an alliance of nonprofit, non-governmental organizations that are involved in international volunteer and internships programs. IVPA promotes excellence and responsibility in the field of international voluntarism and encourages public understanding of and access to international volunteer programs. This website is a great place to begin research into the variety of volunteer programs available. You can search by field of interest, country, and time availability. It also provides fundraising tips and preparation information.
Go VolunteerAbroad.com hosts a number of programs across the world and acts a hub for information about volunteer oppertunities offered world-wide.
Global Service Corps
Child Family Health International (CFHI)
Cross Cultural Solutions
Operation Crossroads Africa
Foundation for Sustainable Development (FSD)