This is kinda fun....

The UPC Database online. Plug in a UPC and see what it belongs to. You can also add UPCs that are not in the database. It knew what my copy of H&R Block TaxCut was, but I had to add the Brita filters we just bought (though it did know that it was form the Brita company). There is also and interesting (to the geekish type anyway) explaination of what the numbers in a UPC mean.