I have used an older version from Dynamic Drive with the same idea. Mine of course was more rough around the edges, but this is a great function using JQuery.

In this post I’ll show you how can you create fancy accordion menu using jQuery. In this post, you’ll see two examples of accordion. First menu’s visibility get’s toggled on clicking on the header while the another menu’s visibility get’s toogled when mouse is moved over it.

http://roshanbh.com.np/2008/06/accordion-menu-using-jquery.html

He does a great job of explaining how he did this and really what makes it so nice is the code is already broken up for you. You just have to plug it in where you want to use it and boom, you are set to go.