Sphinx is an open source full text search server, designed from the ground up
with performance, relevance (aka search quality), and integration simplicity
in mind. Sphinx lets you either batch index and search data stored in an SQL
database, NoSQL storage, or just files quickly and easily - or index and
search data on the fly, working with Sphinx pretty much as with a database
server.

Homepage:
http://www.sphinxsearch.com/
