Ruby on Rails Tutorial
http://ruby.railstutorial.org/

The Ruby on Rails 3 Tutorial book and screencast series teach you how to develop and deploy real, industrial-strength web applications with Ruby on Rails, the open-source web framework that powers top websites such as Hulu, GitHub, and the Yellow Pages. The Ruby on Rails 3 Tutorial book is available for free online and is available for purchase as a PDF download (which also includes a free copy of the Ruby on Rails 2.3 Tutorial book). The Rails 3 Tutorial screencasts contain dozens of tips and tricks to help you go beyond the Rails Tutorial book, including debugging hints, test-driven development techniques, and solutions to many of the book’s exercises. And though the screencasts are carefully edited, I’ve left in some of the problems I encountered along the way, so that you can learn how to recover from the inevitable application errors—and see that even experts sometimes make mistakes. This will be added to Tutorial Resources Subject Tracer™.