Apparently you can now enter any tracking number into the Google search engine and it will take you to the tracking information page no matter what company it's through.
http://www.slashdot.org/fizz writes "Well, Google has done it again. This time, simply enter any tracking number or id number into the Google search box, and Voila! You have a link to the shipper and tracking information. They have a funny little mom/son tech talk bit on the blog about this."