Geo.data.gov
Find and use geographic data.

ICPSR
"Through the Iowa Social Science Research Center  , The University of Iowa maintains membership in the Inter-University Consortium for Political and Social Research (ICPSR), which is operated by the University of Michigan. This membership enables members of the University community to obtain a vast array of data for secondary data analysis regarding economic, education, health, international, legal, legislative, political, and other areas of social research."