The World Society for the Protection of Animals shares information on what someone can do to help animals while vacationing in different parts of the world (compassionate traveling).
Portal and search site providing information for volunteering overseas through a variety of organizations. See http://www.volunteerinternational.org/resources.html for an excellent list of other Web sites dealing with volunteering abroad.
International Volunteerism Resource Center from Idealist.org
Organization helping travelers to pack 5 pounds of needed supplies and deliver them to community-based organizations around the world. Slogan: "Small Space. Little Effort. Big Impact."
Jayne Cravens offers a cogent look at the various ways people can volunteer outside of their home countries, comparing the different types of programs (especially those in which the volunteer pays to serve and those that do not charge; short-term and extended stays) and linking to many resources.
Socialtours.com is "dedicated to the creation and demonstration of a new corporate concept of linked prosperity," and "a global community supporting social development through tourism."
Blog for anyone considering volunteering internationally, with advice for how to choose the right program and other issues. "A handy resource for gap year students, schoolies and travelers who are thinking to volunteer abroad."