Turn Your Arduino Into a Magnetic Card Reader! : 9 Steps (with Pictures) - Instructables
Bluetooth Reader Writer
Build a magstripe reader from scratch - Make:
DIY Magnetic card reader - Make:
GitHub - carlosefr/magstripelib: Magnetic (swipe-type) card reader library for the Arduino.
Countertop, Mobile, and OEM Transactions : MagTek
GitHub - samyk/magspoof: A portable device that can spoof/emulate any magnetic stripe, credit card or hotel card "wirelessly", even on standard magstripe (non-NFC/RFID) readers. It can disable Chip&PIN and predict AMEX card