Drum is a Reddit / Hacker News clone, built using Mezzanine. It is intended to demonstate some of the non-CMS capabilities of Mezzanine, such as threaded comments, ratings, and public user accounts.
Check out the blog post Building Social Apps with Mezzanine, which contains a detailed walk-through of how Drum was built.
Basic setup:
$ hg clone ssh://hg@bitbucket.org/stephenmcd/drum $ cd drum $ pip install -r requirements.txt $ cp local_settings.py.template local_settings.py $ ./manage.py createdb --noinput $ ./manage.py runserver