Fact checking sites

FactCheck
A nonpartisan, nonprofit site run by the Annenberg Public Policy Center; 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..

Politifact
The Pulitzer Prize-winning Politifact researches the claims of politicians and checks their accuracy.

Snopes.com
One of the oldest debunking sites on the Internet, Snopes.com focuses on urban legends, news stories and memes. They also cite their sources at the end of each debunking.

Lead Stories
Established in 2015, Lead Stories intentionally seeks out viral stories using software and debunks them as fast as possible.

LinkedIn
A professional networking website where you can look up the authors of articles and books to see if they're credible.

The Washington Post Fact-Checker
While focused primarily on political facts, it covers specific claims in-depth and with plenty of cross-referencing.

Veracity (iPhone app)
Double check image sources and see where they came from.

Seeing isn't believing: The Washington Post guide to manipulated video
A terrific overview of the different kinds of faked video and how to identify them.

Poynter: Poynter has developed the International Fact Checking Network Code of Principles. Media organizations can sign up to promote excellence and a commitment to fact-checking. Poynter owns the Politifact brand.