Over the holiday, I whipped up a quick GitHub Post-Receive Hook for use with Pivotal Tracker. This is just a small web service, implemented in Sinatra. It was my first time using Sinatra, so any suggestions on improvements are of course welcome (as are they in general, this is open source). I've put the code up on GitHub in the somewhat painfully named tracker_github_hook repo.
The service supports multiple GitHub repos and Tracker projects, so you can run a single service that integrates multiple projects. The service will figure out which commits go to which projects based on a config file on the server that associates a GitHub repo URL (make sure to use the http version of the URL, not https), to a Tracker project ID. For example:
You will need to take care of running the service within your particular server setup. I'm personally running it via Thin/Rack, behind Nginx. I have it setup on the same server that runs our continuous integration system, so these two are differentiated by subdomain.
It should be noted, I will not claim this thing is secure. You run it at your own risk, etc.
Aside from getting the service running on your own server, you'll need to add the URL to it as a GitHub post-receive hook for each project you want to integrate. To do that, go to the Admin tab of your GitHub repo, and then the Services tab. At the top you'll see where you put the URL in. The URL is just the root of the service. Also see GitHub's docs on post-receive hooks as it illustrates just how I built this, how to set it up, etc.
Hopefully others find this useful. Or, what I really hope is that the Pivotal guys get with the GitHub guys and add a standard integration service, where it's automatically configured on the Tracker side, and you just need to turn it on on the GitHub side much like the other service integrations.