For example if you are using Feedburner-->Publicize-->Socialize service, there is option to add a twitter account to your feeds. The URL's in your feeds will be indirectly shortened by Goo.gl while posting to Twitter account.
I have added this blog to my Feedburner account and socialized it via twitter.
http://twitter.com/deepumohanp this is my twitter account, you could see some URL's with 'http://goo.gl' in it. Those URL's are automatically shortened by Goo.gl and then posted to twitter from Google Feedburner.
There an option for using Goo.gl using extensions in Google chrome browser. There in no official release as on 04 Jan 2010. Use this link https://chrome.google.com/extensions/search?q=goo.gl to get a set of Google Chrome extensions that used goo.gl. I am using
goo.gl shortener + share on twitter and is happy with it. Try and explore on all extensions and find yours.
Have nice time.