https://www.catholicvolunteernetwork.org/
Database of 200 domestic and international volunteer programs that typically provide stipend and living costs in exchange for volunteering.
http://www.habitat.org/cd/hr/jobs.aspx?type=7
Variety of international volunteer positions. Some provide housing in exchange for volunteering. Others require monthly fee - less expensive than many volunteer programs.
http://www.volunteerabroad.com/search.cfm
Comprehensive on-line aggregate of international volunteer positions, teaching positions, and jobs abroad. Most volunteer listings are fee based.
http://www.wwoof.org/
In return for volunteer help, WWOOF hosts offer food, accommodation and opportunities to learn about organic lifestyles. Very minimal fee.