== Module ==
# User authentication mixin for use with Rails controllers.
module UserAuthentication
  # Try something like this ...
  def self.included(controller)
    controller.extend(ClassMethods)
  end
  
  # This thing is really a class method of the controller
  # Put all class methods into a ClassMethods module, and
  # the included method above extends the controller with
  # these class methods.
  module ClassMethods
    def authentication_required(options = {})
      before_filter :authentication_required_filter, options
    end
  end 
end

== Controller ==
require_dependency "user_authentication"

class UsersController < ApplicationController
  include UserAuthentication

  authentication_required :except => "login"
  role_required :admin, :only => [ "edit", "update", "destroy" ]

  def index
    list
    render :action => 'list'
  end

  # ... snip other methods
end