We are an Italian Drupal agency and since 2011 are running http://test.drupalskills.org/ a free Drupal quiz community.
Every quarter we introduce 3 levels of questions (10 questions per level), we created an algorhytm to calculate the scores and the ranking considering numer of attempts, time to finish, number of backwards navigation and so on.
The iniziative was quite successful, we have +10K active users but we need:
1) contribution to the questions
2) rebuild a new website with new functionaties and stronger performances.