Vertical Menus

Is there any component (MenuBar seems to be strictly horizontally rendered) or add-on that would allow me to create a menu like MenuBar, but where the items are stacked vertically rather than horizontally?

Previously, we used a Tree to implement this, but it lacks the auto-pop-out/pop-in type functionality. We found that the hierarchical nesting was nice, but after selection, it wouldn’t just pop-in again, and also it seemed that the user had to click the arrow to open/close, etc.

The behavior of the MenuBar is perfect, but we’d like to go down the left side since most screens are wider than they are tall, so we’d like to use that space on the sides rather than the top.

We’re using Vaadin 7.