oishikazuo

Self Shortener is a WordPress plugin to be able to handle URL shortening 
feature, by your WordPress site itself.
Self Shortener can:
<ul>
<li>create short URL using your site URL.</li>
<li>generate random short URL key, by specifying key length.</li>
<li>specify fix URL key instead of random generating.</li>
<li>handle I18N message. Currenly supports English and Japanese.</li>
</ul>
See http://giraffy.jp/products_en/wordpress/selfshortener/ . 
(In Japanese, http://giraffy.jp/products/wordpress/selfshortener/ )

Self Shortener

URL Shortener handled by your WordPress site itself.

MarcusPope

A WordPress plugin that converts all URL formats to root-relative URLs to enable seamless transitioning between staging/production host environments and debugging/testing from mobile devices, without the use of hackish tactics like textual find-replace strategies or risky hosts/NAT spoofing strategies.
With Root Relative URLs you can browse your development site from http://localhost/ or http://127.0.0.1/ or from a named network resource like http://mycomputername/ without worrying about links redirecting you back to your site’s URL.
This plugin also modifies the tinyMCE hooks so links and media embedded with built-in tools will only insert URLs from the first forward slash after the domain (i.e. the root of your site.) This means when you push content changes to a staging or production environment they are guaranteed to reference the correct target instead of accidentally referencing a production resource in development or, worse-yet, a development-exclusive resource in production.
It supports path-based MU Installations, but does not support domain-based MU sites due to architectural deficiencies in the WordPress core.
Version 1.5 fixes an infinite redirect problem that is a result of a core bug in WordPress. If you have problems with the <!–more–> tag or permalinks for custom post types, please read the FAQ or new Install Steps for support.
Version 2.2 allows for adding certain URL’s or partial URL’s to a blacklist, meaning I won’t use root relative urls, but dynamic absolute URLs instead for displaying content. This will fix problems with 3rd party plugins, and can be configured on the General Settings page.
<h3>Arbitrary section</h3>

Root Relative URLs

Converts all URLs to root-relative URLs for hosting the same site on multiple IPs, easier production migration and better mobile device testing.

Self Shortener vs Root Relative URLs