RESOURCES
Try Ruby
Why’s (Poignant) Guide to Ruby
Learn Ruby the Hard Way
RubyMonk
Neo Ruby Koans
Ruby on Rails Tutorial
Ruby on Rails Guides
REFERENCE
Ruby Core API Documentation
API Dock (Ruby, Rails, RSpec)
Ruby on Rails API
Ruby and Rails Docs by Version
Stack Overflow: Ruby
Stack Overflow: Ruby on Rails
Rubular: A Ruby regular expression editor and tester