Recently started work on a new website. We’re using the Kentico CMS, and came across the following while building some search based functionality:
http://www.kentico.com/Docs/DevGuide/smart_search_overview.htm

The lads have integrated their system with a C# port of the lucene search engine library. From what I’ve seen so far, this gives developers really powerful search and sorting options. A summary of some these options can be found here http://lucene.apache.org/java/2_1_0/queryparsersyntax.html.

Like I say, I’ve only started on this, and will update this post when the project is finished.