15 things for a Ruby beginner

From jasimabasheer.com: 15 things for a Ruby beginner.

MacRuby, the definitive guide

The book MacRuby, the definitive guide shows you how to use Ruby and Cocoa on MacOSX for less than 40 Euros.

Ruby One-Click Installer for OSX

Ruby One-Click Installer for OSX.

Programming Cocoa with Ruby

The book Programming Cocoa with Ruby, create compelling Mac apps using RubyCocoa, is a book for the Ruby programmer who’s never written a Mac app before. Through this hands-on tutorial, you’ll learn all about the Cocoa framework for programming on Mac OS X, all for less than 35$ for the paper version and less than 44$ including a DRM free eBook (PDF, epub, mobi).