Is there a cloud based development for Django, such as there is cloud based development and hosting environment for Ruby / heroku
google app engine might do what you want - take a look at it here http://code.google.com/appengine/articles/django.html
Heroku itself is now for Django. It supports Django with the new Cedar "run anything" release.
I now use Heroku for a few django projects. Setup, including adding a postgres DB and deployment is straight-forward, fast, and free or cheap for small projects. I use and recommend AWS S3 (via django-storages) to host static & uploaded files, and running gunicorn if you're using Heroku in production, all of which is pretty simple to setup. Heroku's own documentation for its support for python & django is pretty good. See:
http://devcenter.heroku.com/articles/django
it was sufficient for me, and should get you there and beyond.
You could check out DjangoZoom: "turn your django code into a live, public app in five minutes" on cloud servers. You can currently request an invite for the beta version.
Djangy seems to be similar. I used neither, so I can't say how similar they are. Djangy only supports MySQL as a database, which is kind of a deal breaker for me.
/edit: as Zolomon says, Djangy closed its doors. I'll recommend RJBrady's answer for some serious upvoting.