Opportunity NOC's
Nonprofit organization classifieds    

Idealist.org
Good listings of social service volunteer sites, as well as information on jobs

The Catholic Network of Volunteer Services
Might provide some good leads. Obviously most if not all the leads are with faith-based organizations.     

State of Maine Department of Human Services
   
Essential Information
Links to interesting advocacy and other non-profit organizations    

Nonprofit Career Center
An alpha list of non-prof organizations, plus some pretty cool job listings, mainly from Mid-Atlantic region, a lot in DC    

Human Services Career Network
Your source for Human Service Jobs, Social Service Jobs, Social Work Jobs, Non-Profit Jobs, Mental Health Jobs, and Behavioral Health Jobs.  

 
Social Service.com
Most jobs appear to be in large cities, or West/Midwest, but it's nonetheless an encouraging site.    

New Hampshire Non-Profits

New Hampshire Social Service Agencies
   
Care.com 

Find Child Care, Tutoring, Pet Care, and Senior Care Jobs and Providers

New England Jobs.org/Non-Profit Collaborative

Jobs in social services and political/social advocacy