Ruby on rails Rails is a full-stack, open-source web framework in Ruby for writing real-world applications with joy and less code than most frameworks spend doing XML sit-ups
OpenWFEru is an open source Ruby workflow and BPM engine
ruby-doc.org, includes: “Help and explanations on why Ruby may be the best choice of programming languages.”
37signals.com produced serious enterprise applications with RoR.
Try Ruby - This site lets you type ruby commands into a little console in the browser window. No installation needed, just a browser. Follow their tutorial! It gives a pretty good, quick run-through of Ruby programming principles.
Why’s (Poignant) Guide to Ruby - Online book that is an easy read.
Getting Started With Ruby by Gavin Sinclair
Programming Ruby, The Pragmatic Programmer's Guide by David Thomas and Andrew Hunt
Everyday Scripting with Ruby: for Teams, Testers, and You companion website for the book
JRuby's "complete" JAR for OS X App Bundles – “Now this is really cool. Tony Hursh, commenter on the previous “Advanced Rails Deployment” post, put together an OS X Application Bundle template that allows you to use the JRuby “complete” JAR file as the base of a typical OS X app. What does that mean? That means you just toss the complete JAR into this template, code up some Ruby code, and have a nice dock icon and menu bar like any other app. You can ship the entire app as a bundle, with JRuby as the built-in Ruby interpreter.”
Distributing Rails Applications – “RubyScript2Exe “transforms your Ruby script into a standalone, compressed Windows, Linux or Mac OS X (Darwin) executable. You can look at it as a “compiler”. Not in the sense of a source-code-to-byte-code compiler, but as a “collector”, for it collects all necessary files to run your script on an other machine: the Ruby script, the Ruby interpreter and the Ruby runtime library (stripped down for this script). Anyway, the result is the same: a standalone executable (application.exe).”