We released the first version of the Pivotal Tracker API a couple of months ago, and already there is a growing list of useful 3rd party tools out there:
Pivotal Tracker for Ruby
This is a ruby wrapper for the API, written by our friends at Mobile Commons.
Also from Mobile Commons, this tool allows your to automatically create Tracker stories from inbound emails.
GitHub Post Receive Hook
This is web service that you run on your own server, written by Chris Bailey. It automatically updates stories in your project(s) based on GitHub commit comments:
Synchronize stories in Pivotal Tracker with Cucumber features. If you haven’t heard of it yet, Cucumber is a really cool app that can execute plain-text documents as automated functional tests.
There are more, most of them live in GitHub:
If you have written something you’d like to share, or know of other useful tools, let us know! Also, we’re planning on making the API better, and would love your feedback.