Have you heard of Cappuccino? It's Cocoa for the web. You don't write javascript, you write Objective-J. It's pretty awesome. As a mac developer, I was immediately able to jump in and do cool stuff with it.

I'm not sure what the current state of the framework is, since the company that made it has been acquired, but it sure was a cool idea.

http://www.cappuccino-project.org/