Earlier this year the Pew Forum on Religion and Public life conducted a survey on religious knowledge among the American populace. The newly released results were not surprising, to me at least. In the 32 question survey atheists and agnostics scored the highest, closely followed by Jews and Mormons who were way ahead of the average Christian believer. There's a summary of the results here.
To test yourself, click on the image for a shorter sample of the questions asked. I scored 14 out of 15 and am kicking myself for dithering over the one I got wrong rather than going with my first thought.
The New York Times reports
On average, people who took the survey answered half the questions incorrectly, and many flubbed even questions about their own faith.What is it about religion that suppresses what should be no more than basic general knowledge?
Those who scored the highest were atheists and agnostics, as well as two religious minorities: Jews and Mormons. The results were the same even after the researchers controlled for factors like age and racial differences.