I quickly ported the FlashPunk community UI recently and started building on top of the framework they built. Actually it diverged a bit from the original but I think for the better. The biggest change is that the NineSlice class is now extends from Graphic so that it can be drawn easily each frame.
At the moment I have buttons, checkboxes, radio buttons, text fields, and panels working. I'll see what I can do about a scrollbar and menus but I haven't had a chance to hash them out yet. Although I think the code is flexible enough that most anything is possible.
You can pick up the code on GitHub and take it for a spin. Just to give you and idea of what's possible I'll present you with a flash version of the framework.