From the Why Didn't We Think of This? department... isnoop.net has a Universal Package Tracking tool that allows you to punch in a UPS, FedEx, USPS, or DHL/AirBorne tracking number into a single field, and the tool figures out which type of tracking number it is and generates an update as to where the shipment is, and an RSS feed so that you can receive updates to the shipment via your favorite feed reader.

Even cooler, the site has employed the Google Maps API to show the actual geographical progress of your package. This is definitely a slick use of the Google Maps API, and it sure seems like package tracking was meant to be this way.