It's a human tendency to stay with people and groups that tend to think like you do. This is well and good, but especially nowadays it tends to reinforce political ideas and feeling into mental concrete. We all know people who only get their news from Fox and Power Line, or from Daily Kos and Air America. The fairly obvious problem with this is, of course, that news that detracts from the other side is highlighted and emphasized and news that detracts from your side is minimized and hidden - even to the extent of bad or false reports that are easily debunked. Recall two such stories earlier this year - Dan Rather's Memogate (pushed and defended by liberal blogs), and the Terri Schaivo memo from from Mel Martinez ("debunked" and never admitted to be a Republican memo by most conservative blogs). This fashion of thought in lockstep only solidifies the hyper-partisan tone of most people, where their party is right or right no matter what.
But for thinking people, who haven't been brainwashed into brain forfeiture, this doesn't work. We need to get out to sides we don't agree with and see what they're saying, to see if we can actually defend our position without retreating to the Maginot Line of "well, the other side said it so it has to be wrong." This doesn't mean we need to stroll to the dark and violent no-man's-land of the freepers or the Democratic Underground - after all, one can study diseases without swallowing a vial of the deadly creeping crud.
I've tried to link to some sites that aren't Democratic/liberal - Andrew Sullivan, Balloon Juice, and The Moderate Voice, all mentioned over there in my bare-bones blogroll. (Yes, yes, I know I said that I'd be adding some bells and whistles. And I will, sometime - just not right now.) (I also want to add that I still view myself as a independent moderate - I just find so much more to complain about from the Republican side right now. This does not mean I've swallowed the Kool-Aid of Party Uber Alles.) I also read William Buckley's books, and George Will's columns, and check on columns from Townhall.com. I even get e-mails from Billy Graham and various other religious sites, even though I am an agnostic. (I also get e-mail from Perkins's Family Research Council, but I consider that more of enemy intelligence.) However, as stated before, I don't feel that need to read everything from a side. For example, I will never read anything by Ann Coulter, since she has nothing of value to add when I want intelligent discourse. Now, if I need venom and slander and libel and general frothing, sure - but you know, I find I rarely need that.
So I recommend that whatever viewpoint you have, you take time to find intelligent website from the other side to see what they think as well. I hope my links are a good starting point for that. O also recommend PunditDrome (linked as well to left), which aggregates a bunch of political sites all on one place.
Remember, if your only defense against the other party's ideas is "Well, they said it so it can't be right!" - that's not a defense; it's an excuse, and a lame one at that.