"It's a hoot... Limbaugh has his people monitor FR for his 'stack-of-stuff'. Howie Carr often refers to what's 'being said' on FreeRepublic.... if it's worth knowing... IT'S HERE."
And Tony Snow also checks out FR; and, in fact, responds to posts on the Tony Snow Talk Show Thread every day (which is great). I think Sean and Mark Levin also at least lurk (IIRC Mark posts from time to time as well).
I went to DU once about a year ago, but after reading a couple of posts, I had to get out fast. It wouldn't surprise me if the 'hosts' on Airhead America check out and post on DU for their talking points (not to mention getting them from DNC faxes). Also, I believe Rush pointed out that the NY Slimes and others and the Dim congresscritters get their talking points from Daily Kos.