You can get IBuySpy skin and mojoguidetogalaxy from the community downloads page, both have this kind of menu.
This kind of menu is hard to implement well for different browsers and its also not very user friendly. Its difficult to mouse your way down through a deep hierarchy. Thats why nowadays you see more use of a horizontal menu combined with some kind of vertical or tree view menu.
I do have one new skin, coming in the next release with this kind of menu, named mitchinson-earthy, but I don't like this menu for the reasons mentioned so I also implemented mitchinson-earthy-alt1 with a different menu structure.
Hope it helps,