Apple Developer Connection:
Ruby is a dynamic programming language that, over the last few years, has enjoyed enormous popularity, thanks in part to the Rails web framework. Now with MacRuby, you can create Mac OS X applications with Ruby while maintaining the peformance benefits of a fully fledged Cocoa application. This article will show you how to get started with MacRuby and build your first sample application.
Interesting, including syntax extensions for Objective C's Smalltalk-style method names.