You might find James Bennett's book "Practical Django Projects" helpful:

http://www.apress.com/open-source/python/9781430219385

https://bitbucket.org/ubernostrum/practical-django-projects/...

It talks about Django's apps focus and tries to get one out of the habit of "dumping it all in one app in the project".

Eric Holscher wrote an article about Reusable App conventions:

http://ericholscher.com/projects/django-conventions/app/