Use MongoDB with Django but also use relational database
You could use django-nonrel which is a fork of Django and will let you use the same ORM.
If you dont want a forked Django you could use MongoEngine which has a similar syntax otherwise just raw pymongo.
I'm working on a Django application that needs to interact with a mongoDB instance ( preferably through django's ORM) The meat of the application still uses a relational database - but I just need to interact with mongo for a single specific model. 
Which mongo driver/subdriver for python will suite my needs best ?