ICPSR (Interuniversity Consortium for Political and Social Sciences Research): maintains a data archive of more than 250,000 files of research in the social and behavioral sciences. ICPSR is a unit within the University of Michigan Institute for Social Research and its office is in Ann Arbor. UM-Dearborn is one of ICPSR's 760 member institutions. Check out their Overview & Mission page for more information.
PEW Social and Demographic Trends: Datasets from studies of behaviors and attitudes of Americans in key realms of their lives
Professor Aronson's List of Quantitative Datasets