“neutered” CueCat USB barcode scanner. I bought this on eBay for about $10 and plan to use it to build a book collection database in Books. I've tested it out and it works great. It's not like a grocery store scanner where you can just wave it in the general direction of the barcode and it will scan. Instead, you have to drag the CueCat across the barcode from left to right. Here are the directions that came with it: Hints for Swiping a Barcode:

1. Hold the barcode reader between your thumb and forefinger like a pen or pencil.
2. Place the nose of the cat in the white area on the left side of the barcode, not within the barcode itself.
3. Align the cat's paws with the bottom of the barcode. Move the barcode reader smoothly from the left to the right across the entire barcode and into the white area past it.
4. Keep the reader in contact with the barcode throughout the swipe for an accurate read. Be quick! The faster and more constant the speed of the swipe, the better your results.
5. If the barcode doesn't read, swipe in a back and forth motion a few times. Be patient. It may take a little practice to get the hang of it. Once you have it down, it becomes second nature.

I'm posting the directions because if you try using the CueCat in any other way it just won't work. I think the secret is in holding it like a pencil. Now I just need to find the time to scan all the books and get them organized. Maybe after my final final... tomorrow!