American Fact Finder (U.S. Census Bureau)
DataCite (search engine)
World's largest collection of social science research data.
Search for statistics from 70+ Federal statistical agencies.
Google Data Set Search
Search engine dedicated to finding data repositories on the web.
Pew Research Center
Access free data and reports documenting the impact of technology on American life.
Statistical Abstracts 1870s-2010s (U.S. Census Bureau)
Contains brief biographical information on "28,000 notable men and women who have shaped our world from ancient times to the present day. The dictionary can be searched by birth years, death years, positions held, professions, literary and artistic works, achievements, and other keywords."
GUIDE: Biographical Perspectives
Funk & Wagnall's New World Encyclopedia (via Badgerlink)
GUIDE: What about Wikipedia?
No Sweat Tech: Finding Old Instruction Manuals for Free Online (The Saturday Evening Post, August 19, 2019)
Open Street Map
A map of the world, created by users and free to use under open license.