Dynamenu is an add-in box which will display your categories as a DTHML horizontal drop-down or vertical fly-out menu, an expandable/collapsable tree menu, or even as plain vertical or horizontal menus. The main file includes easy to set options to set the type of menu you desire and the way it behaves. With dynamenu, you can even opt not to display it in the usual "box" so that it can be seamlessly integrated with your store template for a truly custom look!
Sorry, can't post a link to a demo, but if you search Google for Dynamenu or PHP Layers Menu, it won't be hard to find ;)
A forum thread has been started here:
for your feedback, questions or if you want to show off your new menu!