Ruby and Ruby on Rails are growing in popularity. I've been spending a lot of time with them lately. Here are some good sites to get started with Ruby and Rails:
If you are completely new to Ruby, check out this brilliant online Ruby IRB session. It is a way to try Ruby even if you don't have it installed on your computer already. A cleverly-designed interactive tutorial in your browser:

There is an older Ruby tutorial with good information.
Programming Ruby is a great book. The online version is free, but it is an older version. I recommend buying the latest edition which is different than the free online version.
Chris Pine's original Learn to Program is a good introduction.
A fun, but slightly eccentric introduction to Ruby can be found on Why's (Poignant) Guide to Ruby.
The Little Book of Ruby is a free PDF ebook about how write Ruby programs.
Get a free Ruby Cheat Sheet and check out this online reference.
Rolling with Ruby on Rails is a good introductory tutorial. Part 2 is here.
Programming Ruby is the standard textbook on Ruby.
The Ruby Cookbook is helpful.
Also try Ruby for Rails by David Black.
[I've been really busy lately which is why I haven't been posting more often. I will finish this post later. Sorry for the sparse content. If you have resources to add for Ruby beginners, post a comment and I'll add them to this page.]
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