YUI3.4.0 introduces the new Y.Panel widget. I wrote the widget for the library and one of the reasons was to allow developers to leverage it when making cool windowing components for their apps.
Then, I was introduced to some cool iOS-style modal boxes from the Flow web-app and wondered if something similar could be achieved using YUI3 Panel. Well, after a bit of CSS hacking, I think it can.
I haven't finished the entire example yet, so I won't put all the code up yet. You can browse the source but it's a little messy, I haven't got around to cleaning it up yet.
Follow me on Twitter to get notified of when I put everything up. Actually, now that I think about it, I'll probably put it on Github.