While many of these are available at Tutt in paper, they are also online:

Census of Population and Housing

• Full-text decennial census from 1790 forward

County and City Data Books

• County and City Data 2007 and State and Metro 2010 (PDFs and csv)

• County and City Data Book 2000 (PDF)

County Business Patterns Online

• include # of establishments, payroll, # of employees

Current Population Survey

• monthly survey for national and state estimates
• labor force characteristics  also enrollment, income, experience, benefits, etc.
• by age, sex, race, marital status, and education & by occupation, industry, etc.

TIGER/Line Geodatabases -several file types for mapping census geographic data based on data (Census)

CensusScope - easy use - manipulate data or explore demographic trends, maps, charts and tables (University of Michigan)

Census 2010

• Explore Census Data search 
• State & County QuickFacts- areas with more than 5000 people

In addition to the decennial census, the bureau conducts other surveys which provides detailed demographic information between each census.

• American Community Survey - annually (except during decennial census year); 48 questions to randomly selected households throughout the U.S. providing data about income, education, household type and makeup, race and ancestry.
• 2007 Economic Census - profiles U.S. national and local economies every 5 years
• Other Census Bureau surveys and information

Census Bureau programs can be split into 2 broad categories:

1. Demographic

• Historical Statistics Of The United States, 1600s - current, annual time series of the U.S. population, economic indicators, social conditions, and government (CC and in-library use only)
• Census Bureau Historical data - selected population and housing counts (various formats)
• National Historical Geographic Information System - aggregate census data and GIS-compatible boundary files for the US, 1790-2010.