taxonomy_dropmenu builds a (DHTML/CSS) dropdown menu for selected
vocabularies. It allows too to add fixed links, for example, for Home or
Glossary.

The menu is rendered by calling the function taxonomy_dropmenu_buildmenu. You
should have a phptemplate based theme. A example calling code (as a patch) is
provided for box_grey theme

The client should have Javascript enabled in his browser.
