Map Light.Org - Find an Interest Group - Directory
http://www.maplight.org/map/us/interest
Legislator's contributions received by interest groups: Go.
Open Secrets .Org
http://www.opensecrets.org/
Open Secrets web site provides current information on the money American politicians
raise and spend and the money which special interest groups contribute to politicians
About.Com - Issues, Organizations, and Interest Groups
http://usgovinfo.about.com/blorgs.htm