[zelly]

Elastic Search

Lucene

Sphinx

Solr

And thousands of other ones made by hobbyists, but those are the mature (as in since the 90s) ones. For instance Craiglist uses Sphinx.

[mrweasel]

For a quick search engine it's hard to beat Sphinx. I especially love that you can just point it at a database and give it a query and it will just work.

[snikolaev]

> For instance Craiglist uses Sphinx

Actually Manticore Search (fork of Sphinx)