"The oldest and largest fact-checking site on the Internet, one widely regarded by journalists, folklorists, and laypersons alike as one of the world’s essential resources."

"A nonpartisan, nonprofit “consumer advocate” for voters that aims to reduce the level of deception and confusion in U.S. politics. [They] 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."

An independant media outlet that's dedicated to "educating the public on media bias and deceptive news practices." They have an excellent list of "Questionable Sources" and identify where major news outlets are situated on the political spectrum.

Hoaxy is a tool that lets you "visualize the spread of claims and fact checking." You can see how particular claims are spreading versus fact checks.. The data are obtained from public tweets that include links from their list of sources and fact-checking organizations.

"PolitiFact is a fact-checking website that rates the accuracy of claims by elected officials and others who speak up in American politics."

A website and Sunday column in The Washington Post that's purpose "is to 'truth squad' the statements of political figures regarding issues of great importance, be they national, international or local."