One thing I do know is that there is a fair amount of evidence that Fox News puts a blatant rightist spin on their news.
See here:
http://www.outfoxed.org/
Secondly, no one has been so upset about CNN "leaning left" that they tracked down past employees and company memos and things of that nature. Thats gotta say something about Fox's news reporting.
And for a laugh:
http://maddox.xmission.com/c.cgi?u=bill_oreilly