How to a top navigation menu like that of wpmudev.org?

Hi,
I really like the the top navigation menu used here, on this very site (e.g. plugins / themes / development / support / menu) with the way the sub-menu is displayed. Very neat to way to help visitors around the site.
Where could I get the code for this? Is there one of the templates that does it, from which I could get some inspiration?

Thanks,

Thibault