You could probably implement this entirely in CSS. It's a one-layer menu, so using display:none combined with a hover element could hide and show the stuff.
The problem is figuring out just what you're going to put into that menu. Nielsen's point is that these aren't single-list menus: they're complex and serve multiple purposes at once. So figure out what your menu's going to do before you do anything.
I've never done this before: consider this entirely speculation. However, I'd probably use relative positioning. This is speculation - I haven't opened Coda to try this - but perhaps make each top button a div that reveals its child content when it's being hovered over. That way, there's no confusion over where the drop-down menu's going to appear. It might be a little tricky fitting the things that appear under the drop-down menu, but since relative positioning allows for overlaps, I'd say that this would be a fairly simple issue. Drop-downs in CSS aren't particularly difficult: they just get more complex the more children you add.
The problem is figuring out just what you're going to put into that menu. Nielsen's point is that these aren't single-list menus: they're complex and serve multiple purposes at once. So figure out what your menu's going to do before you do anything.