The SEN-11096 is a simple three track magnetic card reader with serial output from SparkFun.
This reader connects to your computer with a DB9 for serial and a PS/2 for power and outputs a 9600bps 8N1 ASCII serial stream. Plug the reader into a serial port (or USB to serial converter), swipe your frequent shopper card, and you'll see the account number plain and unencrypted on the screen. We couldn't find a card the reader couldn't read. No drivers needed. No software needed. Just pure, wonderful serial.