Free CSS Drop-Down Menu Framework does not only separate HTML from CSS, but even CSS definitions are categorized into structural and thematic types. Thus creating a new drop-down means creating only a new theme since structure is permanent.

Your unordered List can be transformed by changing class name only. Available transformations including horizontal, vertical left-to-right, vertical right-to-left, horizontal linear and horizontal upwards. Free CSS Drop-Down Menu is cross browser that there are some configurations available for Windows Internet Explorer 5 or later, Mozilla Firefox 1.5 or later, Opera 7 or later, Apple Safari 2 or later.

Requirements: Internet Explorer 5+, Firefox 1.5+, Opera 7+, Apple Safari 2+
Demo: http://www.lwis.net/free-css-drop-down-menu/
License: GPL License