WikiTribune - Evidence based journalism, from the founder of Wikipedia
Apache Lucene - High-performance, full-featured text search engine library written entirely in Java.
Wikipedia - Wikipedia is a free online encyclopedia, created and edited by volunteers around the world and hosted by the Wikimedia Foundation.
Six Degrees of Wikipedia - Find the shortest path between two subjects
Wikiverse - An interactive galaxy of Wikipedia knowledge ✨
Sphinx Search - Sphinx is an open source full text search server, designed with performance, relevance (search quality), and integration simplicity in mind. Sphinx lets you either batch index and search data stored in files, an SQL database, NoSQL storage.