cheat sheets.

ApplicationController helpers in views 
(putting the methods in ApplicationHelper only makes them available to views,
if you need them in controllers AND views, define them in ApplicationController
and use the helper_method method)
in ApplicationController: 
  helper_method :method_name1, :method_name2, :so_on_and_so_forth

View Helpers in Controllers or Models
(might make you feel dirty, but if you need to you'll get over it)
1. make a module in /lib:
  "shared.rb"
  --
  module Shared
    def shared_help
      SharedHelper.instance
    end
	  
    class SharedHelper
      include Singleton
      include ActionView::Helpers::TextHelper
      include ActionView::Helpers::UrlHelper
      include ActionView::Helpers::DateHelper
      include ActionView::Helpers::TagHelper
      include ActionView::Helpers::NumberHelper
      # and whatever else you need ...
    end
  end
	
2. include the module in a Controller or Model:
include Shared

3. call your view helpers like 'shared_help.method', i.e.:
shared_help.mail_to(email_addr)

View helpers in email templates
use the helper method in your mailer class, like:
class Notifier < ActionMailer::Base
  helper :application
  # ... your mailer methods
end