Sources

http://www.rootsandshoots.org/ is a website that focuses on community service projects organized and led by the world's youth.  Roots and shoots is a Jane Goodall institute, so the projects usually have something to do with improving the earth for both animals and humans.  The main mission of the site is to enhance understanding among different cultures, ethnic groups, religions, and socioeconomic levels.  The roots and shoots program is active in almost 100 countries.

Sources

 Greater Philadelphia Cares is a website that has information regarding various volunteer projects in the Philadelphia area.  I'm also subscribed to their weekly newsletter and event list-serve.

http://www.gpcares.com/

 Volunteers of America is a national, non-profit, faith based organization.  The website helps volunteers look for an area of interest; the site features over 15 categories dealing with issues like homelessness, mental health, and substance abuse.

http://www.voa.org/