tr.im.it 1.2 for Mac is available as a free download on our software library. The application lies within Theming Tools, more precisely General.
From the developer:
Dashboard widget that uses the tr.im API to make long URLs short. Automatically grabs the URL from the frontmost Safari tab. Hit "Trim It" and the trimmed URL is automatically copied to your pasteboard.
What's new in this version:
Added API key to requests at the behest of the good folks at tr.im
You may want to check out more software for Mac, such as Doit.im, I'm Away - IM status changer or IM for Facebook, which might be related to tr.im.it.