http://rubymonk.com/ - Free, interactive tutorials to help you discover Ruby idioms, in your browser!
http://tryruby.org - Another free, interactive tutorial for the Ruby language in your browser!
http://rubykoans.com/ - Once you've got a little Ruby experience, the Koans walk you along the path to enlightenment in order to learn Ruby. The goal is to learn the Ruby language, syntax, structure, and some common functions and libraries.
http://curriculum.railsbridge.org/ruby/ - A step-by-step tutorial site. There are ruby, basic rails and intermedia rails tutorials (site link on the upper right)
http://apidock.com/ruby - API with helpful notes