FLAMENCO stands for FLexible information Access using MEtadata in Novel COmbinations and is an open source faceted browser framework. It is developed in Python and uses Lucene and MySQL to give developers a framework to develop browsing interfaces for collections. There are some nice demos, from which the image above was taken (it is from the Nobel Prize Winners demo and I chose to see only women winners.)
We experimented with a faceted browser for the second generation of the McMaster Museum of Art Online Roman Coin Collection. The model works well with smaller and visual collections, but with items that are harder to represent in small representations we need to think about visual cues. How, for example, might we represent a web page as a small icon in a visual browser so that you can recognize it? Stan Ruecker has been working on interesting models.