Ruby
Ruby is a dynamic, open source programming language with a focus on simplicity and productivity. It has an elegant syntax that is natural to read and easy to write.
Site: https://www.ruby-lang.org
Books
Ruby Web Dev: The Other Way
This guide is an attempt to describe the way to build the web app with a real understanding of each component, with knowledge that is relevant in any web language and framework. To become a better web developer and demand for a better ecosystem!
Developing Games with Ruby
At day you have to wrangle with legacy code, fix bugs, struggle with APIs, deploy services and integrate things. Yet you wish you could create worlds, animate dragons, break laws of physics and design artificial intelligence. You can.
Learn Ruby The Hard Way
This book instructs you in Ruby by slowly building and establishing skills through techniques like practice and memorization, then applying them to increasingly difficult problems. By the end of the book you will have the tools needed to begin learning more complex programming topics.
Better Specs
Better Specs tries to fill this gap by collecting most of the 'best practices' that other developers learn through years of experience.
Sinatra Book
This is a quick recipe book about how to create a Sinatra's project and deploy it into Heroku's platform.
Kestrels, Quirky Birds, and Hopeless Egocentricity
Raganwald's collected adventures in Combinatory Logic and Ruby Meta-Programming.