Flamenco Search Interface Project
Here's how they describe their project, but I'd recommend just taking a look - it might be easier to catch on that way! (in a nutshell - so far they have two great visual information databases you can search - and that makes it special in my book).
"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, guide the user toward possible choices, and to organize the results of keyword searches."