The primary Ruby web site is http://www.ruby-lang.org/, where you can download Ruby distributions and find links to documentation.
Programming Ruby: The Pragmatic Programmer's Guide
Dave Thomas, Chad Fowler, and Andy Hunt. Pragmatic Press: 2004. ISBN: 0-974-51405-5
Ruby Cookbook
Lucas Carlson, and Leonard Richardson. O'Reilly Media: 2006. ISBN: 0-596-52369-6