For monitoring the media for conservative bias, the obvious site is
www.mediamatters.org for the left-leaners. But what is the leading watchdog which looks for liberal leaning decite or inaccuracies? A quick search found MRC, thatliberalmedia, and NewsBusters, but is there anything closer to mediamatters on the right?
I found the sites above to be different than mediamatters in that they seem sarcastic and not as focused on actual missed facts. For instance, on MRC one mainstream reporter noting that the idea of a liberal MSM bias was a myth was cited as liberal bias in the MSM, while liberal opinion pieces without lies or misrepresetation were strangely cited as liberal bias. Other sites were not really fact-checkers or watchdogs.
If such an equivalent does not exist, I suppose my initial explanation would be that the left really has no equivalent to talk radio and the FNC, which provide a lot of the worst offenses cited by mediamatters. Still this answer does not satisfy since many examples of missed facts or very misleading misrepresentations which favor the right are identified in the MSM by mediamatters as well.