If you mean "Component" as in a Rails feature, it's my understanding
that Components are deprecated and will be removed soon.
If you mean "component" in the generic sense, I've seen most Menus
done primarily thru CSS; easiest way to find out is to go look at some
code. There are lots of free CSS/XHTML templates out there that are
nicely done. Do a google search; or go look at http://www.minimalistic-design.net/.
I'm not pushing their site; it's just that I got one of their free
templates and I am quite happy with it.