Conrad Wise - Chat with the biggest brain on the planet!
Apache Lucene - High-performance, full-featured text search engine library written entirely in Java.
botwick - Build your own SMS-based text bot
Six Degrees of Wikipedia - Find the shortest path between two subjects
Sensay for Slack - Get advice from a helpful human, now available in Slack.
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.