Some web sites (such as Slashdot.org and reddit.com) track the activity of users by assigning a score to each user. This score is incremented whenever the user contributes to the web site in some way. User scores can be utilized in a variety of ways. For example, you can release new features to your most active users first, or provide other advantages to active users, which will motivate other users to contribute more to your web site.
Implementing the user scores is pretty simple. You need a data model to maintain scores in the database. After that, you can use the Django model API to access and manipulate scores from within views.