It appears that all sides of the political spectrum must be watching:

http://www.mediabistro.com/tvnewser/ratings/april_ratings_fnc_beats_cnn_and_msnbc_combined_115179.asp

How's this for cable news domination - Fox News beat CNN and MSNBC combined in every hour from 6amET to MidnightET in both Total Viewers and the A25-54 demo for April 2009.

FNC had the top 11 cable news programs in Total Viewers and 12 of the top 15 in the demo. FNC is the #2 network in Total Viewers on all of cable.

From 9amET on, every program grew by more than 60% in the demo. The 5pmET hour, now occupied by Glenn Beck, is up 212% in the demo and up 128% in Total Viewers. Your World with Neil Cavuto is up 102% in the demo and up 60% in Total Viewers. On the Record with Greta Van Susteren is up 75% in demo and up 55% in Total Viewers. Also in demo: FOX Report is up 75%, Special Report 70%, The O'Reilly Factor 74% and Hannity 64%.

Fox & Friends has now been #1 for 90 consecutive months, Studio B with Shepard Smith for 80 consecutive months.

It appears that USA and Nickelodeon have overall top viewership (USA for primetime and Nickelodeon for the entire day overall):

http://tvbythenumbers.com/category/nielsen-weekly-network-tv-ratings/top-cable-networks