When you try to delete an object, the Django admin gives you a list of all the related objects that will be cascade-deleted as a result. What if you want to get a list of these objects programmatically? You could do it this way:

from django.contrib.admin.util import NestedObjects
from django.db import DEFAULT_DB_ALIAS

obj = ...  # the object you are going to delete
collector = NestedObjects(using=DEFAULT_DB_ALIAS)
collector.collect([obj])
print collector.nested()

This gives you a nested list of the objects that will get deleted if you delete obj. Note that NestedObjects is an undocumented API, so there is no guarantee that it will continue working from version to version. I tested only with Django 1.4.1.