Here are sites that can help you determine the truth of politicians' statements:
"FactCheck.org is a nonpartisan, nonprofit “consumer advocate” for voters that aims to reduce the level of deception and confusion in U.S. politics. We monitor the factual accuracy of what is said by major U.S. political players in the form of TV ads, debates, speeches, interviews and news releases. Our goal is to apply the best practices of both journalism and scholarship, and to increase public knowledge and understanding."
"FlackCheck.org is the political literacy companion site to the award-winning FactCheck.org. We provide resources to help students recognize flaws in arguments in general and political ads in particular."
FactChecker (by the Washington Post)
"Checking the truth behind the political rhetoric."
PolitiFact.com (by the Poynter Institute)
"PolitiFact is a fact-checking website that rates the accuracy of claims by elected officials and others on its Truth-O-Meter."
"The definitive Internet reference source for researching urban legends, folklore, myths, rumors, and misinformation."
Fact Checks (by the New York Times)
"The latest fact checks of politicians and public figures."