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.

florianluce

With Shortener URL Redirect, You don’t have to do anything! 
When you publish a new post, page or custom post type, a short url is generated. You can share it, and it will redirect the user to the long url page. It’s invisible to him! 
This plugin does not use any external service.
example: 
https://your-site.com/ab2CdF redirect to https://your-site.com/my-categorie/my-post-name
optimisation available:
<ul>
<li>Create a short URL for each new publication (post, custom post types, page)</li>
<li>Redirect short URL to long/default URL</li>
<li>Display the short link to copy on admin publication</li>
</ul>
Notes: 
This plugin is actually not tested with: 
* Multisite network 
* Translate plugins 
* Other plugins

Shortener URL Redirect

Generate short url for all posts, custom post types and pages to redirect your user to the long URL. No more long URLs share!

GentleSource Short URL vs Shortener URL Redirect