Ruby on Rails is an open-source project hosted at www.rubyonrails.com. This site not only hosts a great de al of code but also much documentation, demos (including movies) and mailing lists for Rails enthusiasts.
Download the latest copy of Gems from RubyForge, at rubyforge.org/frs/?group_id=126.
As of this writing, there is no printed book about Rails. However, the Pragmatic Programmers have released a beta version of the book they intend to publish in late summer 2005 in PDF form. The latest information about both the book and its current status are available at http://www.pragmaticprogrammer.com.
O'Reilly's “OnLamp” site has published several articles about Ruby 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.
If you are interested in a printed reference, the book Programming Ruby: The Pragmatic Programmers' Guide, written by Dave Thomas and published by the Pragmatic Programmers, is an excellent starting point.
The WEBrick home page is at www.webrick.org. A nice tutorial on WEBrick, including how to write servlets, is available at rubyurl.com/N3dPn.
“Exploring Ruby on Rails” by Ara Howard and Doug Frame, www.linuxjournal.com/article/8217