Rails app(project):Django project, Rails Engine:Django app

Bonus: directory layouts, since they're conceptually connected:

http://guides.rubyonrails.org/getting_started.html#creating-...

http://www.deploydjango.com/django_project_structure/index.h...

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The other important point on large scale Rails architecture is that common functionality can/should be extracted to Rails plugins, which can then be turned into Ruby gems.

http://guides.rubyonrails.org/plugins.html

Great Rails project: https://github.com/diaspora/diaspora which uses MVCP (Presenter)

The other bit it to make use of concerns in Rails 4 for extra DRY controllers and models:

https://stackoverflow.com/questions/14541823/how-to-use-conc...