Hello everyone --
I made something for myself and suspect that other people might find it useful, too.
I like to have a copy of the Ruby and Rails documentation handy, even in the rare instances when I am not connected to the internet. I used a Ruby gem called sdoc (which generates documentation that is searchable and combinable) to generate and combine the documentation for Ruby and Rails -- because I can't always remember if a particular method is defined in Ruby or comes from Rails.
You can download everything here:
http://db.tt/z2YhjrL9 (zipped, about 12mb). Once it's downloaded, unzip it wherever you like and open the "index.html" file in your favorite browser. (And while you're looking at it, make a bookmark so you can come back to it easily.)
Enjoy!