Leaderboards are an effective way to show a user quickly where they currently stand within a gamified system. A fun example is the Gamification Gurus leaderboard from the company Leaderboarded. Each month they release an update that shows who has been active in the gamification world that month. It is a great example of a leaderboard being used in isolation – without all of the points and badges that are often associated with simple gamification.
Many blogs and websites these days make use of a comment system called Disqus to manage their comments. It has a few plug-ins that you can easily add to your site if you are using it for comments. One is a Top Commenter’s box. If you look at my blog, you should see it in the side bar. It shows people, at a glance, who is posting the most comments on your pages.