show static under menus once in a page

Hi,
First of all, thanks a lot for that greatly customisable theme.

I explain that blurry title...
I have a 2 level menu with 5 categories and pages inside.
I have drop-down menus working perfectly well when rolling over categories.
Now, when I'm in a page for a category, I wish to display the other pages for this category, in a static way, under the menu.
See http://www.apple.com/iphone/ for example

Any idea how to do that ??

Wordpress 2.9.2 and Atahualpa 3.4.6

Thx...