Where to put the other files

module.rb

module ActionControllerExtra
  module UserLogger
    def self.included(base)
      base.extend(ClassMethods)
    end

    module ClassMethods
      # Logs that a user requested the current action:
      #
      #   MyController < ApplicationController
      #     user_logger
      #   end
      #
      # The same options for ActionController::Filters are available. For example,
      # to only log the user in the create and destroy actions:
      #
      #   MyController < ApplicationController
      #     user_logger :only => [:create, :destroy]
      #   end
      #
      def user_logger(options = {})
        include InstanceMethods
        before_filter :log_user, options
      end
    end

    module InstanceMethods
      def log_user
        logger.info("#{session[:username]} requested #{controller_name}/#{action_name}")
      end
    end
  end
end

require.rb

require 'rails_extensions/user_logger'

ActionController::Base.class_eval do
  include ActionController::UserLogger
end