Apache Solr - Solr is an open source enterprise search server based on Lucene search library, with XML/HTTP and...
ElasticSearch - Elasticsearch is an open source, distributed, RESTful search engine.
ItemsAPI - ItemsAPI is open source search API for creating mobile and web application
Algolia - Algolia's Search API makes it easy to deliver a great search experience in your apps & websites. Algolia Search provides hosted full-text, numerical, faceted and geolocalized search.
Sphinx (search engine) - Sphinx is a fulltext FLOSS search engine that provides text search functionality to client applications. Sphinx (search engine) - WikiMili, The Free Encyclopedia - WikiMili, The Free Encyclopedia
kvCORE - kvCORE is an online platform that helps the real estate businesses to run their entire enterprise through a single platform.