Data.gov
This site provides access to geospatial datasets from agencies across the Federal government.
Geospatial Platform
Geospatial Platform provides geospatial data, maps, services, and applications from government agencies.
MapStats
MapStats is a clickable map allows users to obtain a data profile for an entity. The profiles include demographic and socioeconomic data from 2000-2009.
The National Atlas Mapmaker
The National Atlas Mapmaker is a map viewer displays Census 2000, 1990, and 1980 data.
National Center for Education Statistics
National Center for Education Statistics offers a map viewer and data tables are available for the American Community Survey (ACS), Census 2000 and 1990.
U.S. Department of Agriculture Rural Atlas
U.S. Department of Agriculture Rural Atlas contains a map viewer with data tables from the American Community Survey (ACS) combined with data from the Census of Agriculture and the Bureau of Labor Statistics at the state and county level.
U.S. Department of Housing and Urban Development (HUD)
HUD offers shapefiles for special tabulation areas that the Census Bureau does not provide.
U.S. Environmental Protection Agency's (EPA) MARPLOT
EPA offers an online mapping tool (MARPLOT) that combines 2010 Census data with EPA and U.S. Geological Survey (USGS) data.
U.S. Library of Congress
U.S. Library of Congress offers an archive for historical and specialty maps.
U.S. National Archives
U.S. National Archives gives the public access to historical decennial census data, including actual census records (only up to and including the 1940 Census; records for the 1950 through 2010 censuses are protected and confidential).