Tonight, Google and I sat down to do some nuts and bold research. Here are my notes. Have anything to add?

PS - Based on what I found, I'm thinking Heroku + MongoLab + PyMongo + Django is probably the best way to get my feet wet, since I'm already comfortable with django and heroku.
I'll be trying this in the near future -- will let you know how it goes.
Cloud hosts for mongoDB:
- MongoLab
- MongoHQ
- MongoMachine -- bought by MongoHQ
Reviews here say MongoLab > MongoHQ w.r.t customer service
http://www.quora.com/Heroku/How-would-I-use-the-mongolab-add-on-with-python
python ORMs for mongo
- mongonaut
- mongoengine
- mongokit/django-mongokit
- pymongo (simple wrapper, no ORM)
- ming
- django-mongodb
- django-nonrel
Strong recc for mongoengine > mongokit, esp for django developers.
http://www.quora.com/MongoDB/Whats-the-best-MongoDB-ORM-for-Python
Says mongoEngine is faster than mongoKit
http://www.peterbe.com/plog/mongoengine-vs.-django-mongokit
Slides also argue for mongoEngine
http://www.peterbe.com/plog/using-mongodb-in-your-django-app/django-mongodb-html5-slides/html5.html
Says that pyMongo > mongoEngine
http://stackoverflow.com/questions/2740837/which-python-api-should-be-used-with-mongo-db-and-django
mongoNaut is clearly not mature -- off the island!
http://readthedocs.org/docs/django-mongonaut/en/latest/index.html
Instructions for setting up django and mongo, if that's your thing
http://dennisgurnick.com/2010/07/06/bootstrapping-a-django-with-mongo-project/
PyMongo documentation
http://api.mongodb.org/python/1.7/faq.html
MongoLab's example of integration, plus a small amount of stackoverflow chatter about it.
https://github.com/mongolab/mongodb-driver-examples/blob/master/python/pymongo_simple_example.py
http://stackoverflow.com/questions/8859532/how-can-i-use-the-mongolab-add-on-to-heroku-from-python
Decision reached!
Heroku + MongoLab + PyMongo