Media bias / fact check dot com
I spent some time researching Media Bias / Fact Check (MBFC). It gets mixed reviews, but it appears to be fairly good compared to other fact check websites. I however, think it is biased to the left.
Wiki actually provides a good summary showing both sides.
Rational Wiki goes into more detail.
The fact that MBFC considers Washington Post Fact Check as a trusted source is telling. WaPo's fact check is horrible. It tends to "fact check" subjective statements as if they were offered as fact. And some of their conclusions seem contrary to their own analysis.