Nuno,
1/ > Is there a .chm version ?
http://delynnberry.com/pages/rails-chm-documentation/
(MacOS X users can read chm files with 'chamonix' Chamonix download | SourceForge.net )
2/ There's also DevBoi, a Firefox plugin that gives easy access to various documentations. http://devboi.mozdev.org/ You can even have it install local/offline version of some docs.
Alain