Faceted metadata search and browse
SearchTools has released a practical article on using faceted metadata to enhance search. It contains some interesting screenshots, and a gentle introduction to the concepts. To quote:
A good solution to these problems involves exposing the facets in dynamic taxonomies, so that the search user can see exactly the options they have available at any time. They can switch easily between searching and browsing, using their own terminology for search while recognizing the organization and vocabulary of the data.
[Thanks to Peter J. Bogaards.]