I just found out about the Flamenco Search Interface Project:
The Flamenco search interface framework has the primary design goal of allowing users to move through large information spaces in a flexible manner without feeling lost. A key property of the interface is the explicit exposure of category metadata, to guide the user toward possible choices, and to organize the results of keyword searches. The interface uses hierarchical faceted metadata in a manner that allows users to both refine and expand the current query, while maintaining a consistent representation of the collection’s structure. This use of metadata is integrated with free-text search, allowing the user to follow links, then add search terms, then follow more links, without interrupting the interaction flow.
I particularly like the Nobel prize winners example.