U.S. Census Bureau:
The USGenWeb Census Project
The USGenWeb site, hosted by Rootsweb, a component of Ancestry.com, is "an all-volunteer project to transcribe census records in a standard format in order to make them available to genealogical researchers on the Internet." It is not directly associated with the Census Bureau or any facet of the U.S. federal government.
Citing Records in the National Archives of the United States,
General Information leaflet No. 17. From NARA.
Clues in Census Records, 1850-1930. From NARA.
Measuring America: The Decennial Censuses From 1790 to 2000. From the U.S. Census Bureau.
Population and Housing Items on the General Census Schedules 1790-2000
Compiled by Grace York, University of Michigan Library, March 2002. Download requires Microsoft Excel.