David MacKay has put the textbook he wrote online for everyone to download in a variety of formats. If you find it useful, consider buying a copy.
A FOSS platform for analysing and visualizing large sets of documents. Designed with investigative journalists in mind but has other uses. Has a plugin system. Can be run as a server or locally (https://github.com/overview/overview-local)
. Designed to run as a docker container (bluh) but running it as-is shouldn't be difficult. Written in scala (wtf?) Seems to use postgres as its back-end.
Website of cold cases pertaining to missing and kidnapped people. Possibly of interest for data mining.