A custom user model integrated with the default Django authentication backend. This is based on the feature added in Django 1.5, which allows you to create a custom user model to replace contrib.auth.models.User. The only pre-requisite for this is Django 1.5; if you have an older version and want to upgrade, look here.
The CustomUser model isn't made to be too different from the default User. The biggest change is the absence of a 'username' field, and the 'email' being used as the unique identifier. The rest ofthe code demonstrates how to use the custom model with existing authentication resources:
django.contrib.auth.forms.AuthenticationForm - basic login form provided by Django
django.contrib.auth.login,authenticate - pre-defined methods to login and authenticate a user
See the Django docs
for more info on customizing contrib.auth