I happen to have a USB one, but it seems a much more complicated affair to get that working without a USB Host shield.
I'll probably rather get an RS 232 one.
Thanks for your input.
If you open up the device, I bet you'll find a TTL serial->USB converter chip. You could hack it and pull the data right from device before it goes into the chip. The two most common serial->usb chips are the PL2303 and FT232.
Doing that will keep you from having to buy another barcode scanner.