here is a post about a useful resource from Virtual Library Cat:
"ARDA, The Association of Religion Data Archives, is a fascinating goldmine of information from researchers, polling and census data, and other reliable sources. ARDA provides free access to quality data on American and world religions. In easy to view format, it quickly presents national profiles and American city statistics, religious group membership and religious freedom data, and recent survey results on beliefs and practices, replete with maps, charts, and reports. The site is fun to explore and an easy way to better understand demographic trends and the current role of religious groups and beliefs as a factor in today's world. It's also a great place to take a study break and learn some interesting and often surprising facts at the same time."