data.census.gov, from the The U.S Census Bureau
Population, housing, economic, and geographic data. Includes the annual American Community Survey.
CensusScope - "an easy-to-use tool for investigating U.S. demographic trends, brought to you by the Social Science Data Analysis Network (SSDAN) at the University of Michigan."
Proquest Statistical Insight
100,000 U.S. government publications from 1973, including census data; state and private sources from 1980, and approximately 2000 documents from international organizations from 1983.
Voting and Registration
For each election the Bureau provides information about registration and voter participation based on the Current Population Survey, a monthly sample survey of 60,000 households.
Current Population Survey (CPS) - a monthly survey of about 50,000 households conducted since 1947 by the Bureau of the Census for the Bureau of Labor Statistics. Topics surveyed include race, income, education, education, family size and structure, etc.
