Reformed Theological Seminary recently made the lecutre series:  Preaching Christ in a Postmodern Wold available via iTunes U.  There are 35 lectures in this series by Dr. Edmund P. Clowney & Dr. Timothy J. Keller.  Be sure to give it a listen.  You can access it here:  LINK.  (iTunes required)

Covenant Theological Seminary has offered many on-line courses for free over the years.  They recently launched the “Worldwide Classroom”.  They have 20+ classes with downloadable audio and study notes.  I like the user-friendly layout.  You can check it out here:  LINK.  (Thanks to Justin Taylor for pointing this out.)

I came across these 2 videos last night.  Both of them are lectures that Daniel I. Block gave at Dallas Theological Seminary back in 2004.  The first is titled:  The Burden of Leadership:  The Mosaic Paradigm of Kinship, the second is titled:  The Joy of Worship:  The Mosaic Invitation to the Presence of God.  Learning from Dr. Block was the highlight of my Wheaton College experience.  Happy viewing.