registrations_controller.rb

class RegistrationsController < Devise::RegistrationsController
  def new
    super
  end

  def create
    layout 'custom_devise'

    twitter_uid = params[:user][:twitter_uid]
    first_name = params[:user][:first_name]
    last_name = params[:user][:last_name]
    email = params[:user][:email]

    user = User.new(params[:user])

    user.services.build(:provider => "twitter", :uid => twitter_uid,
      :first_name => first_name, :last_name => last_name, :email => email)

    if user.save

      set_flash_message :notice, :signed_up
      sign_in_and_redirect(User, user)
    else
      render :action => :new
    end
  end

  protected

  def after_sign_up_path_for(resource)
    if resource.is_a?(User)
      flash[:notice] = "Awesome! You're all signed up."
      user_path(resource.username)
    else
      super
    end
  end
end

routes.rb

  devise_for :users, :controllers => { :registrations => "registrations",
    :sessions => "sessions" }

  devise_scope :user do
    get "signin", :to => "sessions#new"
    get "signout", :to => "devise/sessions#destroy"
    get "signup_email", :to => "registrations#new"
    get "user/edit", :to => "devise/registrations#edit"
  end