Current version of my cheat sheet.
Will post at my web site shortly,
with any feedback that comes my way.

Module File
-----------
filename: <name>.rb
example:  functions.rb

Contents
--------
module FUNCTIONS
   def some_function(argument, ...)
      ...
   end
   module_function :some_function
                # ^^^ You specify a name (a symbol)
end

Flat Install
------------
   Copy to site_ruby/<version>
   example: /your/ruby/1.8.4/lib/ruby/site_ruby/1.8

   Usage:
     require 'functions'
     include FUNCTIONS

Nested Install
--------------
   Copy to site_ruby/<version>/<subdir>
   example: /your/ruby/1.8.4/lib/ruby/site_ruby/1.8/etc

   Usage:
     require 'etc/functions'
     include FUNCTIONS