FactCheck.org - aims to reduce the level of deception and confusion in U.S. politics.
snopes.com - fact-checking website. Checks online myths, rumors, urban legends, and misinformation.
politifact.com - rates accuracy of claims by politicians.
Allsides.com - AllSides uses its media bias ratings to provide a breadth of perspectives on today's news, issues and opinions - so you can decide.