These online sources provide a place to start if you are looking for data on religious groups and issues. If you are not finding the information that you need here, contact the subject librarian for assistance.
ARIS is the largest national survey on American religion. This site allows you to download the summary report from 2008, and to access data from the 1990 and 2001 national surveys.
The Berman Jewish Databank @ The Jewish Federations of North America provides access to national, local, and topical quantitative studies of Jews and Jewish communities in the United States and Canada.
The Pew Forum "conducts surveys, demographic analyses and other social science research on important aspects of religion and public life in the U.S. and around the world." Their website provides access to information about issues concerning religion and society as well as demographic data.