Google maps mashup includes data on population, housing cost, housing market, schools, safety, health, climate, income/work, and age ethnicity for the continental US.
annoyingly, their "explains" don't say where the data comes from, so it's hard to know how up to date it is. However, it's neat.
Requires free registration.
Neighborhood Facts provides detailed and the most current information about Denver's 77 neighborhoods. It includes data, maps and graphs about each neighborhood's population, housing, economic and education characteristics, and the health and safety of its residents. It is designed for use by neighborhood residents, policy makers and others who care about Denver's neighborhoods.
Requires free registration.
The Franklin County DataSource is a web-based geographic data application designed to assist human services and community development organizations, funders, government agencies, researchers and concerned individuals in their efforts to understand community conditions and improve the quality of life in central Ohio. The online mapping, reporting and data analysis tools can be used to focus in on a specific zip code, census tract or planning area. Users can also draw comparisons between individual geographies or compare local conditions to the city as a whole. Drawing upon a wealth of social, demographic and real property data, DataSource users have a powerful tool that greatly enhances their ability to identify community needs, plan new programs, allocate and manage resources and target improvements.
Free Registration Required.
Information is at the sub-county level, but only one level beneath county, generally, so Philadelphia is broken only into Planning districts.
Funded by a 3-year grant from the William Penn Foundation, the Metropolitan Philadelphia Indicators Project combines two types of information to illuminate conditions and trends in our 9-county region (defined as the central cities of Philadelphia and Camden along with the Pennsylvania counties of Bucks, Chester, Delaware and Montgomery, and the New Jersey counties of Burlington, Camden, Gloucester and Salem). The first is a set of social, environmental and economic indicators that portray the quality of life in the region’s communities. The second type of information comes from an annual household survey conducted by Temple’s Institute for Survey Research, asking respondents across the region how they assess the quality of life in their communities. Tracking over time the changes in the indicators and in the survey responses, we can better understand how citizens’ perceptions relate to the changing conditions on the ground.


