FRED® API Web Services -- Write programs, build applications that retrieve economic data from FRED® and ALFRED® websites. Customize requests according to data source release, category, series, and other preferences.
United States Census Demographic Maps -- made available by Social Explorer, the site provides a free collection of historical census data maps and reports on the United States from 1940 to 2000.
HUD Office of Policy Development & Research
Liber8 An economic information portal for librarians and students from the Federal Reserve Bank of St. Louis