Who are my potential customers? Where are they? How old are they? How much income do they have? What are their needs and wants?
Government Statistics
The mother of all data sources is the U.S. Census Bureau, with the latest population data from the American Community Surveys (as well from Census 2010) on the American FactFinder. You can narrow your search down by city (or county) to find a profile of general population and housing characteristics, as well as many other details. [http://factfinder.census.gov]
DataUSA (at http://datausa.io) visualizes iindustry and demographic data from the US government.
Maps
PolicyMap displays many popular categories of social and demographic information as colored maps, including population, income, home ownership, education, and neighborhood conditions. [http://www.policymap.com/map]
ZoomProspector will display total consumer expenditures for many major product and service categories. [http://www.zoomprospector.com]