The Carnegie Endowment provides research material on democracy, rule of law, foreign policy, nuclear non-proliferation, trade, the U.S. role in the world, global development , economy and regional issues.
The collection includes federal or state censuses, files based on administrative records, public opinion surveys, economic and social data from national and international organizations, and studies compiled by individual researchers.
World Value Survey Association is an excellent source of national opinion centers national social survey data. This data collection includes survey from over 100 countries. Each national survey has data for at least 1000 respondents.