WordPress.org

The default method of WordPress' implementation of shortlinks adds ?p={post-id} to the end of your site name in place of the full URL. Though this can indeed shorten your link quite significantly; if you have a long site name it still might not be as effective.

This WordPress plug-in allows automatic url shortening of post links with goo.gl URL Shortener using the API recently provided by Google in place of the default ?p={post-id}.

For Example:
WordPress "shortlink": http://christophercochran.me/?p=47 (not so short is it?)
Shortlink created with the goo.gl API : http://goo.gl/Tqczu (I can haz more to say about my awesome link on Twiter now – YAY)