Speaking of conscience as we were just a moment ago, most of you are probably familiar with Andrew Sullivan. He pops up in most serious discussions, not only in the blogosphere but in the MSM as well. Sullivan considers himself a Catholic but he differs strongly from the Church's teaching on homosexual behavior. Sullivan is, or at one time was, generally thought to be a political conservative, but as he allows this issue to color more and more of his thought, he becomes less and less convincing in his arguments. This is compounded by the fact that Sullivan is often a brilliant thinker and writer, which lends his arguments a weight that they don't always merit.
For a good background on Sullivan and where he comes from (philosophically speaking), read this very good post, "The Vicar of Heterodoxy," at the very fine blog Musings of a Pertinacious Papist, which I'll be adding to the blog list shortly. Philip is a fine writer, but even if he wasn't, I'd be adding his blog because of the title alone! ;)
UPDATE: Chris at Veritas has Sullivan's latest "unhinged" screed.