Anything yet, smallbeer?
I don't think it's possible anyway. Because the only way is to use the "hover" property, which can only be applied to "a" in IE. So to have a menu showing when you hover over a link, you'd need nested (!) links.
e.g.: <A HREF="">Caption<SPAN><A HREF="">Item 1</A> ... </SPAN></A>
That's not a) accesible, and b) valid.