• FactCheck.org - From site mission statement: "We are a nonpartisan, nonprofit "consumer advocate" for voters that aims to reduce the level of deception and confusion in U.S. politics."
• Snopes.com - "Welcome to snopes.com, the definitive Internet reference source for urban legends, folklore, myths, rumors, and misinformation."
• Merriam-Webster.com - "For more than 150 years, in print and now online, Merriam-Webster has been America's leading and most-trusted provider of language information."

There are many, many other "fact check" websites out there but most of these are hosted by news organizations or PACs and should not be trusted to be un-biased. Also one should research the topic by reading unfiltered content such as meeting minutes, court logs, peer reviewed papers and other pubished academic papers.

In the end, there is no better fact check than critical thinking skills.