A few years ago I found a paper written by a couple of professors that examined (from an academic point of view) the bias of various news outlets. I think the results will surprise a few here. The first version I read of this paper was written in 2003, but the link here is of an updated (November 2005) version.
The entire paper:
http://www.polisci.ucla.edu/faculty/.../MediaBias.pdf
A brief summary:
Media Bias Is Real, Finds UCLA Political Scientist... 12/14/2005