I found this paper while doing a bit of research for my term work.
"In this paper we estimate ADA (Americans for Democratic Action) scores for major media outlets such as the New York Times, USA Today, Fox News’ Special Report, and all three network television news shows. Our estimates allow us to answer such questions as “Is the average article in the New York Times more liberal than the average speech by Tom Daschle?” or “Is the average story on Fox News more conservative than the average speech by Bill Frist?” To compute our measure, we count the times that a media outlet cites various think tanks and other policy groups. We compare this with the times that members of Congress cite the same groups in their speeches on the floor of the House and Senate. By comparing the citation patterns we construct an ADA score."