I started a little package to wrap the bit.ly URL shortening API in Smalltalk.  It's simple enough to have no dependencies, and works in Pharo and Squeak trunk.  You need a free bit.ly account to use the API.  See BitLyInfo and BitLy class comments, and the specs for more info.

bitLy := BitLy forUser: 'myUsername' withApiKey: 'myApiKey'.
bitLy shorten: 'http://google.com'. "Returns Url: http://bit.ly/h1Bpyx"

Enjoy.
Sean