Here is a recent lecture on George Whitefield from Dr. Thomas S. Kidd delivered on March 25-26, 2014, at the Southern Baptist Theological Seminary in Louisville:
George Whitefield: Lessons from Eighteenth Century’s Greatest Evangelist from Southern Seminary on Vimeo.
Dr. Martyn Lloyd Jones and C. H. Spurgeon both considered Whitefield England’s greatest ever preacher. Dr. Steven Lawson begins to explain why that might indeed be the case in a message entitled “the power of God in George Whitefield’s life.”
Many decades ago, J. C. Ryle wrote the following biography of Whitefield (10 short videos – a great resource):