Three questions before I leave PHP: Formsets, datasources and remote auth

I've been using CakePHP for a long time now and feel comfortable developing sites with it. I do however like Python more then PHP and would like to move to Django.

1) How can I mix multiple models in one form? I know formsets are used for this, but I can't find a decent tutorial on this (views + template). In Cake I can simply to this in my view (template):

echo $this->Form->input('User.title');
echo $this->Form->input('');
echo $this->Form->input('Comment.0.title');
echo $this->Form->input('Comment.1.title');

This would mix a User model, a Profile model and add two comments in one form. How to do this with Django?

2) How do you deal with remote auth in Django? Let's say you hold all users in one database on one server, and serve that as a base for user login on multiple other sites?

3) Datasources. E.g. If I want the User model to use Twitter as the source for user data, not my normal database? (but use the database for articles, comments ..)?