Animated rollover menus

I want to create a menu like on the site http://www.pushstudio.com/

Where the options expand when you roll the mouse over and contract when you move the mouse away, and the options underneath move up and down in tandem. I assume it needs ActionScript which I don’t have much knowledge of.

Could anyone point me to a tutorial that deals with this please? I can’t seem to find one, but I’ve seen the effect fairly regularly so someone must know how to do it!

Thanks.