Download plugin: gurl Google URL Shortner (ver 2.1)
Important note: This plugin only functions with Alfred 1.x. It will not work with Alfred 2.
Update: It seems that Mountain Lion has a different version of grep than that available in Lion, and the new version breaks the gurl extension. I have put together version 2.0 of gurl to fix this issue. It has been rewritten to use PHP instead of relying on commandline tools.
Update 2: Version 2.1 of gurl was released today, July 7 2013, to fix bugs addressed by commenters Elvis and flackend. Thanks guys!
When you get a growl notification like this, your new goo.gl shortened URL is in your clipboard ready to be pasted!
Hope you find this useful! Enjoy.
On the other extension: I originally wrote this extension before I was aware that another goo.gl extension already existed. Oh well! :]