Plugins - Acts as Ferret
Add to favoritesActs_as_ferret is a plugin for Ruby on Rails which makes it simple to implement full text search for Rails. It builds on Ferret Ferret which is a ruby port of Apache Lucene . It is a technology suitable for nearly any application that requires full-text search.
http://projects.jkraemer.net/acts_as_ferret/
svn://projects.jkraemer.net/acts_as_ferret/trunk/plugin/acts_as_ferret
Rails' (MIT)
Searching and Queries

Definitely worth of checking. If you can get Ferret gem installed on your hosting it's best(easiest) solution to full text search. Also, railsenvy got great tutorial how to use this plugin at http://www.railsenvy.com/2007/2/19/acts-as-ferret-tutorial
Hope it helps,
dk