This is an interesting interview with Robert Putnam and David Campbell. I laughed at this part, though:
We found a very high level of tolerance and open-mindedness across religious lines. Americans overwhelmingly believe that people of other religions can go to heaven, and that doesn’t mean just Methodists saying that a few Lutherans are going to make it into heaven. Large numbers, the majority even, of evangelical Protestants say that non-Christians can go to heaven if they’re a good person.