Faceted Search using Solr – what it is and what benefits does it provide..? by James Spencer (eduserv blog).
From the post:
What is Faceted Search?
Faceted search is a more advanced searching technology that enables the end user to structure their search and ultimately drill down using categories to find the end result they are looking for via the site search. Rather than relying on simple keyword searching, faceted searching allows a user to perform a keyword search but then filter content by pre-defined categories and filtering criteria.
Faceted searching also enables you to gain advanced funcionality like suggested search terms, auto completion on search terms and have associated links to content. This provides users with quicker, more flexible, dynamic and accurate search results.
The post goes on to list the benefits of faceted searching in a very accessible way, explains Solr, uses of Solr by the Department of Education (US), and gives additional examples of faceted searching.
Very high marks for presenting the material at a web developer/advanced user level. Hard to judge that consistently but this post comes as close as any I have seen recently.