SearchSpring - SearchSpring is an eCommerce site search tool.
Apache Solr - Solr is an open source enterprise search server based on Lucene search library, with XML/HTTP and...
SearchBlox - SearchBlox is an out-of-the-box Enterprise Search Solution built on top of Apache Lucene/Solr.
Websolr - Exterprise-grade search powered by open-source Apache Solr.
Hulbee Enterprise Search - Hulbee Enterprise Search is another powerful site search solution that intelligently retrieves information and documents regardless of their source or location.
Decisiv Search - Decisiv is an enterprise search solution enabling users to search multiple repositories at once to access documents, projects etc.