blueinstyle

Display your top commenters or authors in a widget, or you can display anywhere on your blog by pasting this code into your theme: <code><?php if(function_exists('jme_top_contributors')) { jme_top_contributors(); } ?></code>
Version 1.4 includes many user requested features. Check <a href="http://justmyecho.com/2010/07/top-contributors-plugin-wordpress/" rel="nofollow ugc">plugin webpage</a> for details on the update.
<ul>
<li>List your top commenters or authors with the option to display their Gravatar, and several other options.</li>
<li>Choose from 2 formats of the widget, with complete control of styles via css.</li>
<li>Exclude users from the list by email address.</li>
<li>The list uses a cache system for improved performance. List updates only when a post or comment is added, or options updated.</li>
</ul>
<h4>Extra Feature</h4>
<ul>
<li>Add a special Icon next to each of your Top Commenter’s name in their comments to give them a little special recognition for being a regular contributor.</li>
</ul>
Support and Feature request forum at http://justmyecho.com/forums/

Top Contributors

Display your top commenters or authors in a widget.

graemeboy

This is a plugin that I made that shows your top 100 most influential commenters on your WordPress blog, ordered by Alexa Rank (a somewhat accurate reflection of a site’s popularity). It also shows the number of Facebook Shares, and name and email address of the author, so that you can quickly get into contact with him or her. It also shows when last they commented on your blog.
It takes some time for the data to load, so please be patient.
I imagine that bloggers would use this to find out which other influential bloggers have recently been interested in their site, and then they’d be able to get into contact with them, saying something like:
“Hey John,
I noticed that you posted a comment on my site the other day, and I just thought I’d send you a quick email to let you know that I like the content you’ve been posting. Perhaps we could write a guest post for each other sometime? I think that would suit both of our audiences well.
Kind regards, 
Graeme”

Influential Commenters

This plugin shows your top 100 most influential commenters on your Wordpress blog, ordered by Alexa Rank.

Top Contributors vs Influential Commenters