Ruby on Rails is an open-source project hosted at www.rubyonrails.com. This site hosts not only a great de al of code, but also much documentation, demos (including movies), and mailing lists for Rails enthusiasts.
An excellent book about Rails (Agile Web development with Rails) was recently published by the Pragmatic Programmers. Information about both the book is available at www.pragmaticprogrammer.com.
O'Reilly's “OnLamp” site has published several articles about Rub y on Rails. One good introductory article is at www.onlamp.com/pub/a/onlamp/2005/01/20/rails.html?page=1.
The Ruby home page is at www.ruby-lang.org. This page has many links to other sites, including tutorials and documentation for the Ruby language.