ARDA provides a large collection of national and international data, largely but not completely numerical, about religion. Includes information about U.S. denominations and congregational membership as well as religious profiles of various countries, including demographic information and, in some cases, public opinion data.
"Pew Research Center is a nonpartisan fact tank that informs the public about the issues, attitudes and trends shaping the world. It conducts public opinion polling, demographic research, media content analysis and other empirical social science research."
"PRRI (Public Religion Research Institute) is a nonprofit, nonpartisan organization dedicated to conducting independent research at the intersection of religion, culture, and public policy." Includes, among other things, a variety of public opinion research.