You can also use your "project" (effectively: a module with a "settings" module) as an "app" (effectively: a module with a "models" module and a "templatetags" module if you need custom ones) by putting its package name in INSTALLED_APPS and sticking a models.py in it.

Then, if you find a piece which would cleanly separate out into a standalone app, you just have to rip it out, add the extracted app to INSTALLED_APPS and update your imports.