Wiliam Denton has put together a facet-map howto:
“This paper will attempt to bridge the gap by giving procedures and advice on all the steps involved in making a faceted classification and putting it on the web. Web people will benefit by having a rigorous seven-step process to follow for creating faceted classifications, and librarians will benefit by understanding how to store such a classification on a computer and make it available on the web. The paper is meant for both webmasters and information architects who do not know a lot about library and information science, and librarians who do not know a lot about building databases and web sites.”
More on Facetmaps on the facetmap.com site.