PUBLIC MARKS with tags search & floss

Ferret is a high-performance, full-featured text search engine library written for Ruby. It is inspired by Apache Lucene Java project.

Solr is an open source enterprise search server based on the Lucene Java search library, with XML/HTTP and JSON APIs, hit highlighting, faceted search, caching, replication, and a web administration interface. It runs in a Java servlet container such as Tomcat.

Sphinx is a full-text search engine, distributed under GPL version 2. Generally, it's a standalone search engine, meant to provide fast, size-efficient and relevant fulltext search functions to other applications. Sphinx was specially designed to integrate well with SQL databases and scripting languages. Currently built-in data sources support fetching data either via direct connection to MySQL, or from an XML pipe.

A company developping OOS for professional search, semantic middleware, and developer products

Aperture is a Java framework for extracting and querying full-text content and metadata from various information systems (e.g. file systems, web sites, mail boxes) and the file formats (e.g. documents, images) occurring in these systems.