Ronaldo Viscuso has just released a new version of his DHTML Menu Portlet. This portlet generates a DHTML menu for site navigation, with links to pages and subpages from a selected page group.
Stylesheet, height, width, mouse-over behavior, etc. are all configurable via the "Edit Defaults" page, which allows for complete customization for pretty much any desired look & feel....
The portlet, screen shots and installation document are available on the Portal Knowledge Exchange.