American Fact-Finder
Census site, has demographic data by county, city, town or zip code.
United States Census Bureau
Demographic characteristics, total population, social, and economic census data for the U.S. and international locations. Useful in determining market size. To generate data by subject, ethnic groups, or geographical locations use the American FactFinder.
United Nations Demographic and Social Statistics
Demographic characteristics of countries, including population, households, housing, income, health and more.
World Development Indicators
Statistics from the World Bank for almost 600 development indicators, dating as far back as 1960.