Django: "projects" vs "apps"
Try to answer question: "What does my
  application do?". If you cannot answer
  in a single sentence, then maybe you can
  split it into several apps with cleaner
  logic.

I read this thought somewhere soon after I've started to work with django and I find that I ask this question of myself quite often and it helps me. 
Your apps don't have to be reusable, they can depend on each other, but they should do one thing.
I have a fairly complex "product" I'm getting ready to build using Django. I'm going to avoid using the terms "project" and "application" in this context, because I'm not clear on their specific meaning in Django.
Projects can have many apps. Apps can be shared among many projects. Fine.
I'm not reinventing the blog or forum - I don't see any portion of my product being reusable in any context. Intuitively, I would call this one "application." Do I then do all my work in a single "app" folder?
If so... in terms of Django's project.app namespace, my inclination is to use myproduct.myproduct, but of course this isn't allowed (but the application I'm building is my project, and my project is an application!). I'm therefore lead to believe that perhaps I'm supposed to approach Django by building one app per "significant" model, but I don't know where to draw the boundaries in my schema to separate it into apps - I have a lot of models with relatively complex relationships.
I'm hoping there's a common solution to this...