A great resource is www.djangopackages.com, which lists a lot of the notable Django apps out there, including links to their respective repos, popularity ratings, etc..
Another way to find popular projects is directly on GitHub: https://github.com/search?q=django
Finally:
- Awesome Django @ https://github.com/wsvincent/awesome-django
- Awesome Python @ https://github.com/vinta/awesome-python