SciCheck.org, a subpage of FactCheck.org "focuses exclusively on false and misleading scientific claims that are made by partisans to influence public policy."

PolitiFact "tracks who’s telling the truth—and who isn’t—in American politics."

Snopes "is a one-stop shop to fact-check internet rumors."

OpenSecrets.org "is a nonpartisan organization that tracks the influence of money in U.S. politics."

Internet Archive Wayback Machine is a tool you can use yourself to fact-check things you find online.

These resources are recommended in the following article: 

Knutson, Jeff. "Turning Your Students into Web Detectives: Five Vetted Resources Students Can Use to Separate Truth from Fiction Online." Edutopia. George Lucas Educational Foundation, 12 Oct. 2017. www.edutopia.org/article/turning-your-students-web-detectives. Accessed 7 Dec. 2017. 

How do I know I can trust this source? I can click on the author's name and learn more about him. He has a professional background working in this field.