BTW, you might want to have a look at JRuby. While it's still pre-1.0, it's moving along nicely. It will allow you to leverage all your knowledge of the Java class libraries.
I know ruby-doc.org, but the only full specification of the language there seems to be the first edition of "Programming Ruby", which describes an older version of Ruby. There is nothing for the current version of Ruby.
Err.... http://www.ruby-doc.org/
"What do you use for Ruby on Rails?"
Textmate. :-)
http://macromates.com/
BTW, you might want to have a look at JRuby. While it's still pre-1.0, it's moving along nicely. It will allow you to leverage all your knowledge of the Java class libraries.