Charges have been swirling recently (i.e., over the last twenty years... or perhaps decades) that the American media are biased. Here's one journalist's response to those charges.
All in all, it's hard to come up with a quantitative measure of fairness or bias, although some studies have tried.
Instead, let's look at a related question: Are the consumers of media biased? Let's play around with Google Trends.
Fox News is associated with visits to rushlimbaugh.com, newsbusters.org, weeklystandard.com, and searches for Drudge, Rush Limbaugh, and Sean Hannity.
MSNBC is associated with newsweek.com, the Huffington Post, Keith Olbermann, and Daily Kos.
NPR is associated with tnr.com, thinkprogress.org, and talkingpointsmemo.com.
(Yes, I know some of the associations are personalities associated with a given media outlet.)
Whether or not the media outlets are biased, it does appear that the viewers (or readers) tend to travel in disjoint communities. I'd opine that the Fox News community is characterized by conservative pundits, while the MSNBC and NPR communities have liberal pundits.