Former conservative liar David Brock heads up a new watchdog site called Media Matters for America:

Because a healthy democracy depends on public access to accurate and reliable information, Media Matters for America is dedicated to alerting news outlets and consumers to conservative misinformation — wherever we find it, in every news cycle — and to spurring progressive activism based on standards and accountability in media.

I thought Brock’s confession, Blinded by the Right, passed muster and Media Matters looks like it might be a useful resource.
Media Matters would be even more useful if they would turn on an RSS feed.
There’s more at Talkleft and in this New york Times article.