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 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 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.
by Zed A. Shaw - LCodeTHW
The book assumes absolutely no prior programming knowledge and will guide you carefully and slowly through the learning process. When you are done with it you will have the skill to move on to other books about Ruby and be ready to understand them.
by Jeremy McAnally
Covers the Ruby language from the very basics to the advanced topics. Written in a conversational narrative rather than like a dry reference book, Mr. Neighborly's Humble Little Ruby Book is an easy to read, easy to follow guide to all things Ruby.