Desiring God…the gift that keeps on giving…has posted a number of seminars online that John Piper teaches periodically in Minneapolis. Among them: Gravity and Gladness on Sunday Morning: The Pursuit of God in Corporate Worship, as well as sessions from his books Desiring God and Future Grace. Some of them are a little dated, which affects only references to current events, culture and music. Just keep that in mind as you listen to them. The truth itself is timeless.