Sage Stats (library database): includes datasets that span all 50 states and the District of Columbia, as well as all counties, cities, and metropolitan statistical areas dating back more than 20 years. Topics covered include crime, social welfare, population, education, and more. For help, see their FAQs page.
American Community Survey (ACS): an ongoing survey that provides vital information on a yearly basis about our nation and its people, including demographics, housing, economic, and social data
Detroit Crime Viewer: Interactive crime map (currently in beta phase) that shows where and when crimes were committed. Crimes are color-coded and it displays location, arrest category, report number, and charge description of incidents that happened within city limits. Users can filter results by date and crime, crime type, and also select location by police precincts, zip codes, neighborhoods, council districts, or by searching the interactive map.
National Archive of Criminal Justice Data: includes over 2,600 curated studies and datasets. It includes several large-scale and well-known datasets, including the National Crime Victimization Survey (NCVS), the FBI's Uniform Crime Reports (UCR), and the FBI's National Incident-Based Reporting System (NIBRS). For help, see their FAQs and User Support contact page.
PEW Social and Demographic Trends: Datasets from studies of behaviors and attitudes of Americans in key realms of their lives. Includes datasets on Hispanic immigration attitudes and trends from the PEW Research Center's Hispanic Trends Project.