Django Content Type Quick Reference

from django.contrib.contenttypes.models import ContentType

# Get the content type for a given model
ct = ContentType.objects.get(app_label="myapp", model="mymodel")
# or
ct = ContentType.objects.get_for_model(MyModel)

# Get the class associated with the content type
model_cls = ct.model_class()

# Filter the queryset as normal              
queryset = model_cls.objects.filter()

# Get a specific object instance given a content type
ct.get_object_for_this_type(username='Guido')

http://docs.djangoproject.com/en/dev/ref/contrib/contenttypes/