FactCheck.org - A "nonpartisan, nonprofit" research center out of the University of Pennsylvania. Their funding information and funding disclosures are on their "Our Funding" page.
Politics in America - A subscription database available to members of the Goucher College community, Politics in America provides information about members of Congress and the constituencies they represent.
Pro Tip: Profiles include voting records and information about district boundaries.
PolitiFact - From the Tampa Bay Times, this fact-checking website focuses on politics; partners with newspapers, television, and radio stations; and won a Pulitzer Prize in 2009. Find out more about their fact-checking process on their "Our Process" page.
Snopes.com - Billing itself as "the definitive Internet reference source for ... misinformation", Snopes.com double-checks a wide range of claims, from urban legends to Internet rumors.