model.user.rb

require 'digest/sha1'

class User < ActiveRecord::Base
	has_one :company

  attr_accessor :password

   # Validations
   validates_presence_of     :email
   validates_presence_of     :password,                   :if => :password_required
   validates_presence_of     :password_confirmation,      :if => :password_required
   validates_length_of       :password, :within => 4..40, :if => :password_required
   validates_confirmation_of :password,                   :if => :password_required
   validates_length_of       :email,    :within => 3..100
   validates_uniqueness_of   :email,    :case_sensitive => false
   validates_format_of       :email,    :with => /\A([^@\s]+)@((?:[-a-z0-9]+\.)+[a-z]{2,})\Z/i
   # Callbacks
   before_save :generate_password

   ##
   # This method is for authentication purpose
   #
   def self.authenticate(email, password)
     account = first(:conditions => { :email => email }) if email.present?
     account && account.password_clean == password ? account : nil
   end

   ##
   # This method is used to retrieve the original password.
   #
   def password_clean
     crypted_password.decrypt(salt)
   end

   private
     def generate_password
       return if password.blank?
       self.salt = Digest::SHA1.hexdigest("--#{Time.now.to_s}--#{email}--") if new_record?
       self.crypted_password = password.encrypt(self.salt)
     end

     def password_required
       crypted_password.blank? || !password.blank?
     end
end

register.haml

%p.message
	Please fill in the form below. You can also use Facebook or OpenID to register.
- form_for :user, '/register', :id => 'register-form' do |f|
	%p
		= f.label :email
		= f.error_message_on :email
		= f.text_field :email
	%p
		= f.label :password
		= f.error_message_on :password
		= f.password_field :password
	%p
		= f.label "Re-type password"
		= f.error_message_on :password_confirmation
		= f.password_field :password_confirmation
	= f.submit "Signup", :class => 'button'

user.rb

  get :new, :map=>"/register" do
    if params["without_layout"] == "true" then @without_layout = true else  @without_layout = false end
    @user=User.new
    render "user/register", :layout => !@without_layout
  end

  post :create, :map=>"/register" do
    @user = User.new(params[:user])
    if @user.save
      flash[:notice] = 'You have successfully logged in.'
      redirect "/user"
    else
      flash[:notice] = 'There was a problem with your registration. Please try again.'
      redirect "/register"
    end
  end