From our friends at the US Bureau of the Census
USA Counties — has just been quarterly updated and is now available on the web at http://censtats.census.gov/usa/usa.shtml. USA Counties now features more than 5,900 data items for the United States, the 50 states (plus the District of Columbia), and all of the nation’s 3,141 counties and county equivalents, and covers areas such as age, agriculture, ancestry, banking, building permits, business patterns, crime, earnings, education, elections, employment, government, health, households, housing, income, labor force, manufactures, population, poverty, retail trade, social programs, veterans, vital statistics, water use, and wholesale trade. It is the most comprehensive source for data on counties in the United States.
posted by Kevin Stolarick