Peace Corps
The three goals of the Peace Corps are to help the people of interested countries in meeting their need for trained men and women, to help promote a better understanding of Americans on the part of the peoples served, and to help promote a better understanding of other peoples on the part of Americans.

idealist.org
"Action Without Borders" is the group's motto. Idealist.org provides opportunities to get involved in 153 countries. Try their database of jobs, volunteer opportunities, and internships.