Federal Election Commission
The FEC is an independent regulatory agency charged with disclosing campaign finance information, enforcing the provisions of the law such as the limits and prohibitions on contributions, and over seeing the public funding of Presidential elections. Lists contributions to all candidates by state--who contributes (by individual, pac, party, and candidate) and how much. Archives back to 1999.
Minnesota Campaign Finance and Pubic Disclosure Board
View funding reports by candidate, political party unit, political committee and fund, and lobbyists.
From a nonpartisan, nonprofit research group that tracks money in U.S. politics and its effect on elections and public policy. Provides a comprehensive resource for campaign contributions, lobbying data and analysis.