N.T. Wright audio available on mp3 (1996 lectures at Yale):
The Jesus of Myth and History
(Props to the N.T. Wright Page for the links.)
This site, run by the Veritas Forum (which seeks to foster discussions on Christianity and related issues on university campuses), has a good selection of free audio from other cool folks, too, such as Os Guinness and Ravi Zacharias, just to name a couple.