I published SimpleTracker, is a simple service that will accept a tracking number or package id from major shipping companies (FedEx, USPS, and UPS), and spit out an RSS feed which you can then subscribe to in your favorite feed reader (FeedDemon, Google Reader, Outlook, Bloglines, etc).
Oftentimes I’m obsessed with knowing where my packages are and why they aren’t on my doorstep yet. Now I’ll always know, without having to keep visiting the tracking website over and over! :)