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/