Django without additional tables?
Don't install any of Django's built-in apps and don't use any models.py in your apps.  Your database will have zero tables in it.
You won't have users, sites or sessions -- those are Django features that use the database.
AFAIK you should still, however, have a SQLite database.  I think that parts of Django assume you've got a database connection and it may try to establish this connection.
It's an easy experiment to try.
is it possible to write Django apps, for example for internal/personal use with existing databases, without having the 'overhead' of Djangos own tables that are usually installed when starting a project? I would like to use existing tables via models, but not have all the other stuff that is surely useful on normal webpages.
The reason would be to build small personal inspection/admin tools without being to invasive on legacy databases.