you could try suckerfish drop down menus.
http://www.htmldog.com/articles/suckerfish/dropdowns/
but I guess you need to be familiar with the bar html to work with them.
You could just try searching google for javascript drop down menu. Putting the word free in helps too.
They are dhtml is javascript mixed with css, so yes to both.
You can have pure javascript ones, pure css ones (not much browser support) or a hybrid like the one I've linked to above.
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