Steve

This plugin allows you to specify an alternative domain name to use with the built in URL shortening service.
For this to work it requires the chosen domain to be pointed / parked on the hosting account used for your blog.

Custom Shortlink Domain

Customise the domain name used to generate shortlink URLs.

k0nsl

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, if defined in the settings page. The plugin currently use knsl.net as the only service and stores the data in the database of knsl.net.
Plugin homepage: http://k0nsl.org/blog/k0nsl-short-urls-plugin/
For support use WordPress.org or devNET community forums: http://devnet-software.org/
Thanks!

k0nsl Short URLs

Automatically shortens the blog post URL via knsl.net.

Custom Shortlink Domain vs k0nsl Short URLs