Simple config

config.yml

defaults: &defaults
  default_from: foo@mailinator.com
  cdn: false

development:
  <<: *defaults

test:
  <<: *defaults

staging:
  <<: *defaults

production:
  <<: *defaults
  default_from: prod@example.com
  cdn: false

settings.rb

#source: http://openmymind.net/2010/10/18/Weekend-NET-Pains
#copy this to config/initializers
#to use simply type Settings.cdn or Settings.default_from
class Settings
  @@settings = YAML::load_file(Rails.root + 'config/config.yml')[Rails.env]
     
  class MissingSettingOptionError < StandardError;
  end
     
  def self.method_missing(key)
    raise MissingSettingOptionError, "#{key.to_s} is not in the config file" unless @@settings.include?(key.to_s)
    @@settings[key.to_s]
  end
     
end