Some online references for Ruby:
http://en.wikipedia.org/wiki/Ruby language
http://www.rubyist.net/~slagell/ruby/index.html
http://www.ruby-forum.com/forum/4
http://www.klankboomklang.com/category/ruby-internals
http://dablog.rubypal.com/2009/1/14/10-things-to-be-aware-of-in-moving-to-ruby-1-9
http://eigenclass.org/hiki.rb?Changes+in+Ruby+1.9
http://www.artima.com/intv/ruby.html
http://www.informit.com/articles/article.asp?p=18225
http://rubyhacker.com/index.html
http://glu.ttono.us/articles/2005/10/30/why-and-how-ruby-and-rails-unit-testing
http://visibleworkings.com/little-ruby (incomplete but awesome)
http://blog.scribestudio.com/pages/rails
http://www.infoq.com/articles/changing-the-present-case-stud