RubyGems User Guide
Publisher: RubyGems.org 2010
RubyGems is the premier ruby packaging system. It provides: A standard format for distributing Ruby programs and libraries; An easy to use tool for managing the installation of gem packages; A gem server utility for serving gems from any machine where RubyGems is installed; A standard way of publishing gem packages.
Download or read it online for free here:
by Avdi Grimm - objectsonrails.com
The book is documenting some guidelines and ideas for applying classic object-oriented thought to Ruby on Rails applications. It is aimed at the working Rails developer who is looking to grow and evolve Rails projects while keeping them flexible.
Everything from installing Ruby and the basics of the language through to topics such as arrays, file handling and object-oriented programming are covered. Written both for experienced in other programming languages and for novices.
by Minero Aoki
The RHG is a book that explains how the ruby interpreter (the official C implementation of the Ruby language) works internally. To fully understand it, you need a good knowledge of C and Ruby. This book is going to investigate ruby as a whole.
by Huw Collingbourne - No Starch Press
A comprehensive tutorial to the Ruby language. Each chapter is accompanied by ready-to-run source code for all the examples. There is also an Introduction which explains how to use the source code in Ruby In Steel or any other IDE of your choice.