Full Authentication, Authlogic

application_controller.rb

class ApplicationController < ActionController::Base
    
  helper_method :current_account, :current_user # you may have others that go here too

private

  # I added this so that way I can just use current_account just like current_user
  def current_account
    @current_account = Account.find_by_subdomain(request.subdomain)
    return @current_account
  end    

  def current_user_session
    return @current_user_session if defined?(@current_user_session)

    # This line here is the main thing that you need to add. 
    # Notice the current_account.user_sessions.find
    @current_user_session = current_account.user_sessions.find unless current_account.nil? 
  end

  def current_user
    return @current_user if defined?(@current_user)
    @current_user = current_user_session && current_user_session.user
  end
end

user.rb

class User < ActiveRecord::Base
  belongs_to :account
    acts_as_authentic do |c|
    c.validations_scope = :account_id
  end
	
  def self.find_user_and_account(login)
    find_by_email_and_account_id(login, $accountID) # we use the global here.
  end
end

user_session.rb

class UserSession < Authlogic::Session::Base
  # Just telling Authlogic to use our method.
  find_by_login_method :find_user_and_account
end

user_sessions_controller.rb

class UserSessionsController < ApplicationController
  def create
    $accountID=current_account.id # Here is the global
    @user_session = current_account.user_sessions.build(params[:user_session])
    if @user_session.save
        redirect_to dashboard_url, :notice => "Login Successful!"
    else
      render :action => :new
    end
  end
end