The website "Opposing Views" has a good debate on the Christian Nation question. Perhaps it's because of my bias, but I believe the "no" side is clearly winning the debate. The experts are, for the "yes" side, Dr. Paul S. Vickery, History Prof., Oral Roberts University, and for the "no" side, Dr. William Martin, Harry and Hazel Chavanne Emeritus Professor of Religion and Public Policy in the Department of Sociology at Rice University.
Brief notes: Not only did Dr. Vickery cite David Barton for his position, but also a figure named Catherine Millard whose shoddiness puts Barton to shame.
On the other hand, this is my favorite post from Dr. Martin on putting the key Founders' quotations in context. Check out who gets footnote #2 (hint, me).