Speedboxer

This plugin will convert valid <a href="http://twitter.com/" title="Twitter" rel="nofollow ugc">Twitter</a> usernames mentioned in comments into a link to their Twitter profile page. For example, if somebody mentions “@mattfreedman” in their comment, this plugin will check with Twitter to see if the user “mattfreedman” exists (which is does) and when it does, it will convert it into “<a href="http://twitter.com/mattfreedman" rel="nofollow ugc">@mattfreedman</a>“.
Please note: As this plugin converts usernames on the fly (whenever and everytime somebody views the comments), and checks Twitter for every username (to ensure it’s valid), I strongly recommend using a caching plugin such as <a href="https://wordpress.org/extend/plugins/wp-super-cache/" title="WP Super Cache" rel="ugc">WP Super Cache</a>. Which will not only lessen the load on Twitter’s servers, but also speed up page loads.
Although it says this plugin requires WordPress 2.6, I see no reason why it wouldn’t work with earlier versions, I just haven’t tested it with earlier version.
This plugin requires cURL to be installed on your server, and has only been tested with PHP 5.2.x.

Twitter Links

Converts Twitter usernames mentioned in comments (eg. @mattfreedman) with a link to the mentioned user's Twitter profile page.

Jack Reichert

Relying on hit counts simply does not reflect the impact of your posts. SharePulse finds and ranks your site’s posts that have the greatest social impact. The stats are gathered by getting the Twitter share count, Facebook share count, LinkedIn share count as well as your own site’s most commented posts measuring actual engagement. SharePulse lets you display these posts in your site’s sidebar showing off your posts which have had the greatest social impact over the past day, week, month year or for all time. Each post is displayed with the total number of tweets, shares and comments.
Note: This is the alpha for the plugin relaunch. Feedback is crucial, so please don’t hesitate. We have a feature roadmap and <a href="http://sharepulse.net/contact/" rel="nofollow ugc">we want your input</a>.
The Facebook api has been tightened, it may not update each time. I’m working on a fix.
<h3>Settings</h3>
Widget title SharePulse allows you to customize the widget title
Date range: You can choose to display the stats from the past day, month, week, year or all time.
Number of posts to display: You can choose the number of posts to display in the widget. You can preview each option’s stat count from “SharePulse > SharePulse” in the admin menu.
Allow linkback at bottom of widget: We did not ask for payment to develop this widget yet we are sharing it freely, if you like it please show your appreciating by allowing the linkback.

SharePulse

SharePulse ranks in a widget your site's posts which have had the greatest share count, using Twitter, LinkedIn, Facebook and your comments.

Twitter Links vs SharePulse