There are innumerable websites devoted to Ruby, Rails, and related technologies. Here are a few to start exploring.

Ruby language site

http://www.ruby-lang.org/

Ruby documentation site

http://www.ruby-doc.org/

Ruby 1.8 class library reference (online)

http://www.ruby-doc.org/ruby-1.8/index.html

Ruby 1.9 class library reference (online)

http://www.ruby-doc.org/ruby-1.9/index.html

Ruby class library reference (to download)

http://www.ruby-doc.org/downloads/

Ruby on Rails

http://www.rubyonrails.org/

Ruby Inside (information/blog)

http://www.rubyinside.com/

My blog

http://www.sapphiresteel.com/Blog/