I just ran across this series of articles by Bob Kauflin. I can't recommend it highly enough, both for those involved in leading and conducting worship and for those sitting in the pews. Bob Kauflin is a songwriter and worship leader that works out of the Sovereign Grace network of churches. I have very much appreciated his work in songwriting, and we use several of Sovereign Grace Music's songs at our church.
Kauflin asserts that there are several idols that are being worshiped in American churches on Sunday morning - often ignorantly - along with the worship of the one true God. These idols aren't carved images or statues, but rather tend to be other elements of American worship. Kauflin identifies music, tradition, creativity, experience, liturgy, biblical knowledge, biblical ignorance, musical excellence, results, reputation, and relevance as potential idols that can draw our worship away from God. Kauflin confesses that he is guilty of worshiping each of these things before God at one point or another, and I must admit the same.