YOURLS is a free URL shortener service you can run on your webhost to have your own personal Bitly.
This plugin is a bridge between YOURLS and your blog: when you’ll submit a new post or page, your blog will tap into YOURLS to generate a short URL for it.
This plugin also features BuddyPress support. Short URLs can be generated automatically for each member and each group, and are customizable if permitted by the BuddyPress administrator.
Requires PHP 5.
Note: this plugin should still work but is no longer maintained. See http://yourls.org/#More#wordpress
See plugin source or check the SVN commit changelog