One of the preacher/ authors most influencing my thinking currently is Tony Campolo. Back during my "Ditto-head" days, I wrote Campolo off as a bleeding heart liberal. But I then began doing something that most right-wing Christians appartently don't do - I started reading the Bible! Sarcasm aside, it's amazing what reading the Bible will do for your theology and your political views.
I would strongly encourage you to go to Campolo's website and subscribe to his podcasts. You can also enjoy this video from the Colbert Report.