gentlesource

This plugin creates a short URL from the blog post permalink and stores it 
in the database. The URL is displayed below the blog post along with a link 
to twitter that passes the short URL on.
You can use all short URL services that offer an API. Here are a few:
<ul>
<li>http://melt.li/</li>
<li>http://lin.io/</li>
<li>http://unrelo.com/</li>
<li>http://bit.ly/</li>
<li>http://u.nu/</li>
<li>http://tinyurl.com/</li>
</ul>

GentleSource Short URL

Automatically shortens the blog post URL.

karmacracy

With Karmacracy, you have fun while sharing links. Send cool links, while you improve yourself and get relevant: win awards, get domain clips, talk about revelant words as you get clicks sending good kcies, knowing new people and discovering new content. Check karmacracy and have fun!” />
This wordpress plugin will allow you to insert the widget from karmacracy in all your posts with just a button.

WP Karmacracy

Allows you to insert the Karmacracy Widget in your blog in an easy way.

GentleSource Short URL vs WP Karmacracy