Central Intelligence Agency World Factbook & CIA Factbook entries as JSON files

Common crawl: data scraped from the web for anyone to use

Crowd disasters

Etymology database

Foreign Ministers in 13 powerful countries since 1789

Historical datasets

Historical Britain, 1800+

Nobel laureates

Nobel prize

Slave trade (historical)

Small datasets of historical interest for statistics development

UFO reporting (UK)

UFO reporting center (US)

UFO sightings data — National UFO Reporting Center (US)