4 links
A Practical Introduction to Ruby: First Steps
coolnamehere.com
Introduces Ruby to beginners. Treats installing, and writing a first simple script.
Ruby Embedded into C++
metaeditor.sourceforge.net
Describes how to embed Ruby interpreter in C++, gives skeleton to build on, treats concepts of embedding, advanced topics like SWIG. Descriptions, code, diagrams, links, news.
Things That Newcomers to Ruby Should Know
glue.umd.edu
By Bill Tjokroaminata. List of most common 'gotchas' in this language, in HTML, text. Table of contents, descriptions, code samples, links.