acts_as_solr Tutorial: More Search Goodness in Rails
Enter Solr. Solr is an open source 'server' based upon the actual Java version of Lucene which is well known for its stability. acts_as_solr therefore acts as a conduit between your Rails applications and a Solr/Lucene server meaning that you get full 'enterprise quality' search features based on proven software. Micha Wedemeyer has put together a great resource on how to install and setup Solr and acts_as_solr and the official acts_as_solr homepage has examples of how to use it within your own Rails applications.