There are many archives (often subject-related) that collect sets of data.
Data.gov - the main repository for government data. But sometimes going to the various departments can be a quicker way to find specific data and information. A few of the more popular ones are:
Crime data for the nation are derived from Summary Reporting System (SRS) and National Incident-Based Reporting System (NIBRS) reports voluntarily submitted to the FBI.
Data-Smart City Solutions is working to catalyze adoption of data projects on the local government level by serving as a central resource for cities interested in this emerging field. We highlight best practices, top innovators, and promising case studies while also connecting leading industry, academic, and government officials.
ICPSR, hosted by the University of Michigan is the world's largest social studies data archive. Create an account with your Miami ID to get full access.
IPUMS provides census and survey data from around the world integrated across time and space. IPUMS integration and documentation makes it easy to study change, conduct comparative research, merge information across data types, and analyze individuals within family and community contexts. Data and services available free of charge.