Ruby Users Guide
This guide covers the following topic: What is ruby, Getting started, Simple examples, Strings, Regular expressions, Arrays, Back to the simple examples, Control structures, Iterators, Object-oriented thinking, Methods, Classes, Inheritance, Redefinition of methods, Access control, Singleton methods, Modules, Procedure objects, Variables, Global variables, Instance variables, Local variables, Class constants, Exception processing: rescue, Exception processing:ensure, Accessors, Object initialization and Nuts and bolts.
Author(s): Mark Slagell
NA Pages 
Ruby Programming by Wikibooks.org
This book is currently broken down into several sections and is intended to be read sequentially. Topics covered includes: Notation conventions, Basic Ruby, Ruby Semantic reference, Built in Classes, Standard Library.
Author(s): Wikibooks.org
NA Pages
This book is the only Rails book that does test-driven development the entire time, an approach highly recommended by the experts but which has never been so clearly demonstrated before. Finally, by including Git, GitHub, and Heroku in the demo examples, the author really gives you a feel for what it’s like to do a real-world project. The tutorial’s code examples are not in isolation.
Author(s): Michael Hartl
NA Pages
