http://moneyline.cq.com/pml/home.do
Campaign finance news from Congressional Quarterly. Good search features and information on lobbying and lobbyists.
http://www.elections.state.il.us/CampaignDisclosure/Welcome.aspx
Offers current information in a searchable database of campaign contributions and expenditures for the local candidates.
http://www.followthemoney.org
The official site of the National Institute on Money in State Politics. A vast pool of resources related to campaign donations and corporate ties at the state level.
http://www.fundrace.org
Search to see who's donated how much to which party. Via the Huffington Post.
http://www.opensecrets.org
Open Secrets is a nonpartisan guide to money's influence on U.S. elections and public policy.