* The number of religious "Nones" - people identifying themselves with no religion - was right around 1% through the 1950s. In the 1970s it increased from 3-7%, and stayed below 10% through the end of the century. It's now over 20%. In the 1950's, ~70% of people were Protestant Christians. Now it's half that amount.
* In the year 2000, 12% of Americans reported that religion was "not very important" in their lives. Now it's double that amount.
* In the year 2000, 13% of Americans reported that they "never" attend religious services. Now 29% never attend.
For that matter, I know a handful of people (my grandparents age) who aren't really religious but that go to church most weeks 'cause it's a nice social thing.