Extending the Django User model with inheritance

from django.contrib.auth.models import User, UserManager

class CustomUser(User):
    """User with app settings."""
    timezone = models.CharField(max_length=50, default='Europe/London')

    # Use UserManager to get the create_user method, etc.
    objects = UserManager()

...

user = CustomUser.objects.create(...)

# auth_backends.py
from django.conf import settings
from django.contrib.auth.backends import ModelBackend
from django.core.exceptions import ImproperlyConfigured
from django.db.models import get_model

class CustomUserModelBackend(ModelBackend):
    def authenticate(self, username=None, password=None):
        try:
            user = self.user_class.objects.get(username=username)
            if user.check_password(password):
                return user
        except self.user_class.DoesNotExist:
            return None

    def get_user(self, user_id):
        try:
            return self.user_class.objects.get(pk=user_id)
        except self.user_class.DoesNotExist:
            return None

    @property
    def user_class(self):
        if not hasattr(self, '_user_class'):
            self._user_class = get_model(*settings.CUSTOM_USER_MODEL.split('.', 2))
            if not self._user_class:
                raise ImproperlyConfigured('Could not get custom user model')
        return self._user_class


# settings.py
AUTHENTICATION_BACKENDS = (
    'myproject.auth_backends.CustomUserModelBackend',
)
...

CUSTOM_USER_MODEL = 'accounts.CustomUser'

http://scottbarnham.com/blog/2008/08/21/extending-the-django-user-model-with-inheritance/