American Fact Finder (Census Data) - Website contains data obtained from several different censuses and can be searched by city, county, state, town or zip code. Data includes but is not limited to: population, age, race, employment, income, and education.
Bureau of Labor Statistics - Well maintained site. Includes access to government reports and the Occupational Outlook Handbook On-Line.
The Library of Congress - The Library of Congress offers a wide variety of online databases and Internet resources. It provides an easy-to-use gateway for searching other institutions' online catalogs and extensive links to resources on the Internet. You may want to see the LC Research Tools section of the home page (especially THOMAS), which provides full-text access to bills and resolutions under consideration in the current Congress and the two previous Congresses.
Public Agenda Online - The inside source for public opinion and policy analysis. The site has a large amount of information on public opinion. If you're looking for stats on how Americans feel about a variety of issues, you should definitely bookmark this site.