Logitech USB Webcams, How To Get Them Working...
So, it turns out Logitech's webcams that have a manual focus (the "4000" and the "Zoom" models, at least) work fine with Delicious Library, IF you use the correct drivers. This is kind of cool because Logitech's webcams are cheaper than iSights, but, frankly, they're really not as nice: no autofocus, cheap plastic cases, the mounting bracket is plastic and loosens easily, and the image quality is far inferior. But, hey, cheaper. There's probably some expression that sums up the notion of getting more value if you spend more money, but it's beyond me.
Anyways, Logitech cameras ship with drivers from our fine friends at IOXperts, but unfortunately there's a bug in the current version of the drivers, so it crashes (often immediately) with Delicious Library. This bug is fixed in their new beta drivers, but the bad news is, you have to pay $20 for them. (They work for free for 30 minutes, though, so you can test it out.) On the other other hand, if someone gave you their old Logitech camera for free, you might be able to spend $20 and get a working barcode scanner!
Alternatively, you can wait until the drivers come out of beta and they'll be re-posted on Logitech's site, assumedly for free.
To sum up: if you want to mess around with beta software, you can play around with using some Logitech webcams today. Or, if you wait, you can probably get the real drivers in a bit, for free.