Followthemoney.org: learn where politicians receive donations for their campaigns. This site is created by the National Institute on Money in Politics (NIMP).
Influence Explorer: find out how politicians are influenced by lobbying, campaign donations, and more.
Open Secrets: this site reveals where campaign money originates, provides information about lobbying, and analyzes the results of their findings.
Vote Smart: discover all kinds of information about politicians, like biographies, positions, voting record, speeches, and so forth.
MapLight: this organization sheds light on how wealthy individuals and company influence policy and politicians who need campaign donations in order to be successful.
GovTrack.us: this non-governmental organization follows the goings on of the U.S. government. They can help you make sense of current proposals, votes, bills, and other legislative activities.
PollingReport.com: search and browse for poll results on a large variety of political topics.
On the Issues: each political candidate's views on every issue are documented on this website.