Ruby-Lang.org – The official Ruby web site, completely maintained by members of the Ruby community and available in several languages.

RubyGems.org – The home of all Ruby gems.

Ruby Koans – Learn Ruby (and testing) through Koans. Probably the coolest way to learn Ruby right now.

Ruby Learning – Ruby guru Satish Talim’s web site about learning the Ruby language. It contains tutorials, study notes, and even online classes.

Ruby Corner – The most comprehensive Ruby blog aggregator.

Ruby Inside – The Ruby blog, by Peter Cooper.

Ruby Forum – A mirror of the most important Ruby-related mailing lists.

RubyDoc.info – Your one-stop resource for reference documentation. Everything from Ruby core, Standard Library, gems, and even Github-hosted Ruby projects.

RubyFlow – Community-powered link blog. Created by Peter Cooper

The Ruby Toolbox – A collection of ruby resources and libraries, organized by category and popularity.

RubyCommitters.org – List of all the Ruby core committers. Created by Aaron Petterson.

RubyLang.info – “RubyLang.info is a community driven web site, dedicated to helping both new and experienced Ruby developers.”