data.census.gov serves as a gateway to a wide range of data compiled by the Census Bureau. It includes demographic, housing, economic and geographic data from the various Censuses and the American Community Survey.
The decennial census and the American Community Survey provide a rich source of data on population, socio-economics and housing. The first data from the 2010 Census was used to determine congressional representation. Start your search using American Factfinder or the specific data source.