This month Berkley-based non-profit MAPLight.org expanded their coverage of the relationships between interest groups, legislators and votes to include data for US Congress.
MAPLight.org for Congress combines all campaign contributions to U.S. legislators with legislators’ votes on every bill, using official records from the Library of Congress web site and the nonpartisan Center for Responsive Politics (OpenSecrets.org). The resulting database of bills, voting records, and campaign contributions powers the search engine at MAPLight.org and enables people to see the links between dollars spent and votes cast in Washington D.C. [maplight press release]
Maplight is doing some serious legwork to augment the CRP data with industry positions on bills. They are also doing neat things with timelines so that the user can get a better idea of the relations between donations and key votes.
I took a quick stab at creating a network from some of their example California data on a Bottled Water Bill