The Magstripe Track 2 Card Reader based on AVR can be used to view numerics stored a magnetic data card. Although there is no writeback ability, the device is very useful as a card debugger. The treatise will use an LCD character display to relay this data to the user. The circuit uses an AVR microcontroller and can modified to work with similar RISC controllers.
Magstripe Track 2 Card Reader based on AVR: [Link]