Dan Podsedly's blog
There's a new Mac OS X Dashboard widget available that allows you to create Pivotal Tracker stories easily, right from your desktop.
It's written by Thomas Vie, and posted on his blog here:
http://techpolcook.blogspot.com/2009/11/widget-for-pivotals-tracker.html
The widget uses the Pivotal Tracker API. For other user contributed tools and applications, check out the 3rd party tools page.