I am trying to create a menu that pops out, but instead of turning visibility off and on for a

or
• , I want the
  or
  • to slide. I am having problems with it.

using the "hover" in css works great for popping out lower level listitems, but trying to accomplish the same with the onmouseover and onmouseout screws up. 
What is a best practices approach for having menu items slide out or down using jquery or css?  If I could use Css I would prefer to, but I don't know of a way to slide something.

Thanks