Display your top commenters or authors in a widget.
This WordPress plugin/widget will display top commenters of your blog in the form of gravatar images. The images can be stacked up or listed in a side
Add a Disqus combination widget to your WordPress blog's sidebar
Let the games begin! The Comments Leaderboard ranks your top commentators in a way that's sure to spark competition throughout your community.
This plugin shows your top 100 most influential commenters on your WordPress blog, ordered by Alexa Rank.