In the 14 April New Yorker, Jill Lepore offers a review essay examining several recent books on the faith(s) of the founding fathers, including Martha Nussbaum's Liberty of Conscience, Garry Wills' Head and Heart: American Christianity, Frank Lambert's Religion in American Politics: A Short History, Forrest Church's So Help Me God: The Founding Fathers and the First Great Battle Over Church and State, and Steven Waldman's Founding Faith: Providence, Politics, and the Birth of Religious Freedom in America.
The entire essay is both timely and very much worth reading, so I won't summarize it here, but I do want to note Lepore's very apt (if a bit succinct) formulation about the religious tendencies of a few of the major founders: "They approached religion in more or less the same way they approached everything else that interested them: Franklin invented his own; Washington proved diplomatic; Adams grumbled about it; Jefferson could not stop tinkering with it; and Madison defended, as a natural right, the free exercise of it."