Data Sources

This is an evolving list of interesting or unique data sources I've come across.

Books

ABPC Price Guide A searchable database of auction and book sales, jointly owned by the Antiquarian Booksellers' Association of America and Biblio.
WorldCat Enormous catalog of books and other materials in libraries worldwide.
HathiTrust Academic and research instititution partnership providing access to digitized books and other materials.

MatWeb - As searchable database of material properties including data sheets for polymers, metals, ceramics, and other engineering materials.

Engineering Toolbox - Resources, tools, and basic information for engineering and design of technical applications.

Google Scholar - A freely accessible web search engine that indexes the full text or metadata of scholarly literature across an array of publishing formats and disciplines.
Semantic Scholar - A free, AI-powered research tool for scientific literature, based at the Allen Institute for AI.
arXiv - A repository of electronic preprints (known as e-prints) approved for publication after moderation, that consists of scientific papers in the fields of [[mathematics]], physics, astronomy, electrical engineering, computer science, quantitative biology, statistics, mathematical finance and economics, which can be accessed online.

Ethnologue - A comprehensive reference work that catalogs all of the world’s known living languages.
Glottolog - A comprehensive reference for the world's languages, especially the lesser known languages.
SIL International - A faith-based nonprofit organization serving language communities worldwide.
Wikipedia List of Languages - A list of languages by number of native speakers.

OmniGlot - An online encyclopedia of writing systems and languages.

Of particular interest is OmniGlot's Undeciphered Scripts. "The writing systems listed below have yet to be deciphered or have only been partially deciphered. In some cases the writing systems have been deciphered but the languages they were used to write remain a mystery."
Wikipedia List of Writing Systems - A list of writing systems (or scripts), classified according to some common distinguishing features.

Open Context - An open access data publication for archaeology.
Pleiades - A community-built gazetteer and graph of ancient places.
World Heritage List - The United Nations Educational, Scientific and Cultural Organization (UNESCO) World Heritage List.
Atlas of Hillforts - A crowd-sourced database of hillforts in the British Isles.
Atlas of the Historical Geography of the United States - A collection of maps of the United States from the colonial period to the present.
Atlas of the Historical Geography of the Holy Land - A collection of maps of the Holy Land from ancient times to the present.
Digital Index of North American Archaeology (DINAA) - A project to create a comprehensive digital index of archaeological site locations in North America.