ICPSR (Inter-University Consortium for Political and Social Research)
http://www.icpsr.umich.edu/
The ICPSR is the largest collection of Social Science Data in the world. Topics included in the archive include: economics, government, health care, crime, education, etc. This resource is also available via Databases at Emory. The Data Center also maintains an archive of ready-to-use ICPSR datasets which are accessible via the search engine on the Data Center home page.
Leibniz Institute for the Social Sciences (GESIS)
http://www.gesis.org/en/home/
GESIS is one the premier data archives in Western Europe. It is the principal repository for collections such as the Eurobaromter series of polls in European Union members. It also has a variety of historic data sources, such as a large collection of data from the German Democratic Republic and a similar collection of studies for pre-WWII Germany. GESIS is also a member of the Council of European Social Sciences Data Archives.
UK Data Archive (UKDA)
http://www.data-archive.ac.uk/
The UK Data Archive is another of the premier data archives in Western Europe, with a wide-ranging and eclectic collection covering topics such as the finances and trade of the East India Company, the fiscal straits of European governments in the Middle Ages, Orange Order membership in Northern Ireland, and interviews with black immigrants to Britain in the 1800's and 1900's. The UKDA is also a member of the Council of European Social Sciences Data Archives.
Data.Gov
http://www.data.gov/
Data.Gov is a central portal for datasets, both statistical and geospatial, that are produced by the Federal Government of the United States. While the site is not exhaustive in its coverage, it does include data from multiple agencies within the federal government. The data catalog is located at http://explore.data.gov/.
Harvard Dataverse Network (DVN)
http://thedata.harvard.edu/dvn/
Harvard's Dataverse Network is an eclectic collection of datasets and data collections, ranging from replication datasets from articles on topics such as political competitiveness in post-war Latin America or the effect of IMF programs on government spending, to ongoing research projects on topics such as manifestos of regional political parties, to replication archives for academic journals.
World Bank Data Catalog
http://data.worldbank.org/data-catalog
As part of its Open Data Initative, the World Bank has opened up access to dozens of its data collections and compiled into a single data catalog. The holdings here range from larger databases covering multiple topics to more narrowly-focused collections associated with particular research projects.
Historical Statistics of the United States Millennial Edition
http://hsus.cambridge.org/HSUSWeb/toc/hsusHome.do
The Historical Statistics of the United States Millennial Edition is a revised and updated version of the Bicentennial Edition (C 3.134/2:H 62/970) that was published in 1975 and provided statistical information up to 1970. The Millennial Edition has expanded the coverage of the Bicentennial Edition to include data from the 2000 Census (and, with some topics, post-2000 data) and to include topics that were not covered in the Bicentennial Edition (e.g. slavery, poverty, and Native American Indians). The Millenial Edition contains extensive documentation and allows users to create tables of statistics and view them in HTML or PDF format or save them as Excel or .CSV files. Please note that coverage for tables will vary by topic. This resource is also available via Databases at Emory.
Statistical Abstract of the United States
http://pid.emory.edu/v23kn/
The Statistical Abstract contains a wealth of information on numerous socio-economic and demographic indicators for the U.S. Earlier editions of the Abstract back to 1878 are also available as .pdf files. There is also a CD-ROM version of the Statistical Abstract available in the Data Center, and the tables on the CD-ROM version often cover more years of data/statistics than do the print or on-line versions.