State of the Cities Data Systems (SOCDS)
This site specializes on data about cities and metropolitan areas. Some of the data is available at other sites, but here it is in a particularly useful interface. From the 1970, 1980, and 1990 Censuses it includes data on total population, housing and home ownership, race/ethnicity & immigrants, educational attainment, poverty and income, families with own children, and household rent for cities and Metropolitan Statistical Areas. The entire dataset can be downloaded, or one can select different data for different areas for viewing. They also have "Current Employment Statistics" ("employed residents, the size of the labor force, and the unemployment rate during a selected month in two selected years between 1990 and 1999"). Finally, it offers "Special City Extracts from County Business Patterns," which has data from the Census' "Standard Statistical Establishment List (SSEL)."