Robert P. George has written an excellent book on politics and religion: The Clash of Orthodoxies: Law, Religion, and Morality in Crisis. I highly recommend it. I ran across a short 3 minute clip in which he addressed the separation of church and state. See the link below for access to this video.
What should be the relationship between the church and state? Are the people with religious views excluded from participating in the government? Are religious views only for the private sector? What is the true interpretation of the First amendment? These are important questions that are addressed in this video.