General Data Archives

ICPSR - link to this page for all the details about Johns Hopkins Membership in Inter-University Consortium for  Political and Social Science Research

FEDSTATS - Gateway to statistics from over 100 U.S. Federal agencies.(Search by topics using the A-Z list). Will lead to quick statistics as well as datasets, surveys conducted by the various agencies.

FERRET (try the beta release version)
Allows searching of many federal datasets across a single interface. Datasets include: American Community Survey (ACS) American Housing Survey (AHS), Current Population Survey (CPS) National Ambulatory Medical Care Survey (NAMCS) National Center for Health Statistics Infant Death, Survey of Income and Program Participation and more.
 
Data Archives Around the World & selected directory of data sites Council of European Social Science Data Archives. Covers the data archives in several countries

Data Program and Library Services at University of Wisconsin Madison & Its list of other data libraries and archives.
The collection at DPLS includes major surveys from a variety of distributors(including ICPSR), U.S. government data, and locally produced archival datasets. The collection is cross-disciplinary, reflecting research interests in the social sciences. Longitudinal surveys, macroeconomic indicators, election studies, population studies, socialization patterns, poverty measures, labor force participation, public opinion polls, education and health data, and local/national/international governmental statistics are among the subjects represented. 

 University of California San Diego Data on the Net catalog
Search or browse a listing of 748 Internet sites of numeric Social Science statistical data, data catalogs, data libraries, social science gateways, addresses and more.