gistfile1.rb

class User < ActiveRecord::Base
  attr_default      :first_name, 'First'
  attr_default      :last_name,  'Last'
  attr_default      :name_addr,  lambda { "#{full_name} <#{email}>" }
  attr_default      :email,      lambda { organization.default_email }

  def full_name
    [first_name, middle_name, last_name].select { |name| !name.blank? } * ' '
  end

  belongs_to :organization
end

user1 = User.create :email => '[email protected]', :name_addr => ‘Joe <[email protected]>’
user1.name_addr # =>  "Joe <[email protected]>"

user2 = User.new 
user2.attributes = { :first_name => 'Joe' }
user2.name_addr # =>  "Joe Last <[email protected]>"

user3 = User.create :email => '[email protected]'
user3.last_name = 'Doe'
user3.name_addr # =>  "First Doe <[email protected]>"