There’s a free lecture by Kathleen Hall Jamieson here where she talks about the conservative and liberal media and how it reinforces the way we think about the world.  From the abstract:

Dr. Kathleen Hall Jamieson offers a compelling analysis of the conservative media establishment, from talk radio to Fox News to the editorial page of the Wall Street Journal. Using survey data, case studies and the meteoric rise of Rush Limbaugh as evidence, Jamieson tells the story of the growth of conservative media and how it has fundamentally changed American politics. Dr. Jamieson is the Elizabeth Ware Packard Professor of Communication and the Walter and Leonore Annenberg Director of the Annenberg Public Policy Center.

What’s interesting is that she’s talking from a purely factual basis and doesn’t give any normative claims about political thinking.  It’s a very interesting lecture.