Databases for finding USA demographic data include the following:
PolicyMap
Data and mapping tool that provides access to over 15,000 indicators related to demographics, housing, crime, mortgages, health, jobs and more. Data is available at all common geographies (address, block group, census tract, zip code, county, city, state, MSA) as well as unique geographies like school districts and political boundaries. Create, save, download, customized maps and tables, or upload your own data to map.
SimplyAnalytics
A mapping, analytics, and data visualization application that makes it easy for anyone to create interactive maps and reports using thousands of demographic, business, and marketing variables.
Sage Data
Create custom, exportable charts with data points from the US Census, such as age, gender, income, etc.
Social Explorer
Current and historical census data and demographic information: US Census, American Community Survey, religious membership, carbon emissions data, etc. Customizable maps, charts, and reports. Info
American FactFinder (free website)
Data about the United States, Puerto Rico and the Island Areas. Data comes from several censuses and surveys: American Community Survey, American Housing Survey, Annual Economic Surveys, Annual Survey of Governments, etc.