Guidance for a Factory Employee RFID InfoSystem

That should do well enough, but if you can locate the older PS/2 style, you could have a lot more support.

http://arduino.cc/playground/ComponentLib/BarcodeScanner
http://arduino.cc/playground/uploads/ComponentLib/arduino-barcode-code.txt

Adafruit has a tutorial that include a HID mod that could work without the host shield: