Allsides.com: Links to news coverage on the same topics from left, center, and right perspectives. Also offers a Media Bias Chart.
FactCheck.org : This organization checks 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.
Opposing Viewpoints: A Pierce Library-licensed database with pros and cons on many different controversial topics. (Pierce College login required)
Snopes.com : This highly regarded rumor analyzing site has been researching rumors since 1995.
Politifact.com : PolitiFact staffers research statements and rate their accuracy on the Truth-O-Meter, from True to False. The most ridiculous falsehoods get the lowest rating, Pants on Fire.