sudo gem install ruby-openid
ruby script\plugin install open_id_authentication
rake open_id_authentication:db:create

# routes.rb
map.open_id_complete 'session', :controller => "session", :action => "create", :requirements => { :method => :get }

# session_controller.rb
class SessionController < ApplicationController
  def create
    if using_open_id?
      open_id_authentication(params[:openid_url])
    else
      password_authentication(params[:login], params[:password])
    end
  end
protected

  def open_id_authentication(openid_url)
    authenticate_with_open_id(openid_url, :required => [:nickname, :email]) do |result, identity_url, registration|
      if result.successful?
        @user = User.find_or_initialize_by_identity_url(identity_url)
        if @user.new_record?
          @user.login = registration['nickname']
          @user.email = registration['email']
          @user.save(false)
        end
        self.current_user = @user
        successful_login
      else
        failed_login result.message
      end
    end
  end
end