SproutCore UI is a framework that sits on top of the SproutCore 2.0 framework. It's used to build interactive app-like interfaces easily for the web, with a strong focus on mobile platforms. This talk from the July 2011 SproutCore Meetup highlights the project's goals, architecture, and API.
Watch the talk here: http://www.vimeo.com/26454701
Clipping is a handy way to collect important slides you want to go back to later.