I have been going back and forth over which Python API to use when interacting with Mongo. I did a quick survey of the landscape and identified three leading candidates.
You might give django-mongodb-engine a try. It's a backend for Django-nonrel, so you can continue to use Django's models and ORM. It's not yet as complete as the other APIs, though:
http://www.allbuttonspressed.com/blog/django/2010/05/MongoDB-backend-for-Django-nonrel-released