Cascading select menus in Rails?

I’m looking for a canned solution to creating cascading
select menus in Rails. Kind of like optgroup, except that
the lower-level items live in their own menus, as seen in:

Can anyone point me to some nicely packaged technology,
so I don’t have to fight with the JavaScript myself?

-r Rich M. [email protected] +1 650-873-7841

Technical editing and writing, programming, and web development