Don't call your Django application "site" in Google App Engine
This one had me scratching my head for a while today:
I created a Django application called "site" in my project, and although everything was working perfectly locally with the Google App Engine SDK and Google App Engine Django Helper but when I deployed, I got an ImproperlyConfigured error.
Changing the name of the application fixed the issue.
I'm off to file a bug on this...