Check out Sphinx and the amazing ThinkingSphinx gem. Having used both extensively, I greatly prefer Sphinx over Solr.<p><a href="http://sphinxsearch.com/" rel="nofollow">http://sphinxsearch.com/</a><p><a href="http://freelancing-god.github.com/ts/en/" rel="nofollow">http://freelancing-god.github.com/ts/en/</a><p>CollectiveIdea also maintains a good fork of delayed_job for those who are interested in that.