Audio and Video Lectures on the Trinity
Audio Lectures
Wayne Grudem has a four part audio series on the Trinity. 
                             Part 1,Part 2,Part 3,Part 4
Video Lectures

The Forgotten Trinity By Dr. James White
For the Doctrine of the Trinity By R.C. Sproul
The Mystery of Trinity - Monotheism By R C Sproul [Lecture 1]
The Mystery of Trinity - The Biblical Witness By R C Sproul [Lecture 2]
The Mystery of Trinity - Early Controversies R C Sproul [Lecture 3]
The Mystery of Trinity - Fifth Century Heresies By R C Sproul [Lecture 4]
The Mystery of Trinity - Contradiction vs Mystery By R C Sproul [Lecture 5]
The Mystery of Trinity - One in Essence, Three in Person By R C Sproul [Lecture 6]