I'm a big fan of C.S. Lewis. The first book I ever read of his was The Screwtape Letters. I was then too young to really understand what it was all about. Later I began collecting all the C.S. Lewis books I could find, including biographies. Recently, I read his sermon "Learning in Wartime" in The Essential C.S. Lewis, which includes the famous quote,
"Good philosophy must exist, if for no other reason, because bad philosophy needs to be answered."
Christianity Today has an article entitled "What C.S. Lewis Sounded Like", which includes links to recordings of some C.S. Lewis' talks. Click here if you're interested.