Covenant Seminary has a stockpile of great resources, including a ton of mp3s. I have recently enjoyed listening to the set of recordings from the 2005 Sacrifice of Praise Worship Conference, held at the seminary at the beginning of the year. Each of the posted sessions was very good, covering a variety of topics related to worship and the planning worship services.
"Worship as Gospel Re-Presentation," Bryan Chapell's general session talk, was especially good. Chapell begins by tracing the development of Protestant liturgy, from Luther to Calvin to the Puritans and beyond. Although he notes many of the differences between each, his stated goal is to examine their commonalities. The thrust of his session is that a worship service should be structured as a re-presentation of the Gospel. Many different components can be used, but the overall contour of the service is a corporate-level retelling of the work of the Gospel in an individual's life. Chapell uses Isaiah 6 to flesh out this pattern: the prophet comes before God and apprehends His absolute holiness. This sight immediately overwhelms Isaiah with a sense of his own sinfulness. God then makes provision for Isaiah's cleansing, which results in instruction and equipping for service. Similarly, Chapell argues, our worship services should flow from a proclamation of God's greatness into recognition of our own sin, then into assurance over our pardon which comes through the cross of Christ, and finally into instruction in holy living, both as individuals and as a corporate body. From his survey of liturgical forms, Chapell notes that a wide variety of components can be used while still maintaining this basic Gospel contour.
Kevin Twit's talk on "Theology on Fire: The Transformational Power of Hymns" is exceptionally good, as is Reggie Kidd's discussion of "Bach, Bubba, and the Blues Brothers: The Singing Savior's Many Voices." And, as I mentioned, the other sessions provide a great deal of valuable and insightful reflection on corporate worship. The entire set of conference recordings is a great resource to anyone involved in leading and planning worship services, as well as anyone seeking to more clearly define a theology of corporate worship.
(One minor complaint about the site: navigating through the resource library could be a little easier. To find the Sacrifice of Praise conference recordings, you can go first to the topic index page and then to the "View all titles" option. The Sacrifice of Praise Worship Renewal Conference recordings are towards the bottom of the list. Or just use "sacrifice" as a term for the "by title" search function.)