Data, Statistics, and Polling
ATLA Religion Database
The main database for all religious traditions; main coverage back to 1949.
Gallup Poll News: Religion
Trends in views on religion, religious identity, and religiosity in the U.S.
Pew Research Center: Religion & Public Life Data and Resources
Data and polling on religion and religious views, including the U.S. Religious Landscape Survey and the Pew-Templeton Global Religious Futures Project.
U.S. Religion Census, 1952 to 2010
County-level data on the number of of congregations in each county for 236 faith groups.
Association of Religion Data Archives
American and international data collections on religion, submitted by religion scholars and research centers.
World Religion Database
A good source of statistics on religions.