Ruby on Rails resources

Here are some useful resources for Ruby on Rails.
(* not a comprehensive list, references are in no particular order.  The list may grow, or shrink, in the future…)

This is is a useful article for a novice: How to Create a Blog from Scratch Using Ruby on Rails

I found it while reading this article: A Simple Twitter App with Ruby on Rails – Messages With Ajax

How Rails Developers do Ajax (with jQuery) in 2011