City-data is a great site for demographic and geographic data for cities in the U.S. The authors of this site, have compiled satellite photos, stats about residents, geographical data, state profiles, crime data, housing, businesses, weather, hospitals, schools, libraries, houses, airports, radio and TV stations, zip codes, area codes, and user-submitted facts for thousands of cities and towns in the U.S.. Some of the data is dated and you may have to search elsewhere, but no where as conveniently as here.
There is also a City-Data forum where you are free to ask specific questions about a city. For example, I wanted to know what the morning commute time was between two towns in Chicagoland, and I was quickly answered with an accurate estimate by a forum member.
