Apache Lucene - High-performance, full-featured text search engine library written entirely in Java.
Heroku - Agile deployment platform for Ruby, Node.js, Clojure, Java, Python, and Scala. Setup takes only minutes and deploys are instant through git. Leave tedious server maintenance to Heroku and focus on your code.
Six Degrees of Wikipedia - Find the shortest path between two subjects
8base - Rethink development using 8base's low-code development platform.
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.
Porter - Heroku that runs in your own cloud