Economics

Repository of census and survey data collected from sources around the world. Includes social, economic, health, geographic, and education data.

Open to self-deposit by anyone which can make it rather confusing.

Searchable database of U.S. economic data. Created and maintained by the Research Department at the Federal Reserve Bank of St. Louis

The U.S. government's official portal for open data. Provides access to data from numerous federal agencies in open, machine-readable formats, as well as tools and resources to help utilize them.

The United States Census Bureau's official data website. Allows users to access and compare extensive data from the census.

Official website of the U.S. Bureau of Labor Statistics, maintained by the Department of Labor. Provides searchable economic and labor data for the U.S.

International relations conflict data.

The U.S. government's official portal for open data. Provides access to data from numerous federal agencies in open, machine-readable formats, as well as tools and resources to help utilize them.

Web portal for the General Social Survey, a sociological survey that collects information on the opinions, experiences and practices of U.S. residents. Maintained by the University of Chicago's National Opinion Research Center.

Clearinghouse for statistics pertaining to American education from prekindergarten through graduate school. Maintained by the federal Department of Education's Institute of Education Sciences.

Generally national-level, international development data.

Archive of data resources from research in the social and behavioral sciences, including 21 specialized collections of data in education, aging, criminal justice, substance abuse, terrorism, and other fields.

A new tool from Google that searches multiple data sources. However, it does include a large number of results where one has to pay for data, so use with care.