While the latest craze for "secure" projects seems to be RFID, there is something to be said for good ol' magnetic cards. If you're interested in integrating low-coercivity magnetic cards into your project, or just hacking an existing card you already have, this video will show you how.
In the above video, SparkFun CEO Nathan Seidle shows you how to interpret the data provided by both our Magnetic Card Reader and our Magnetic Card Reader/Writer. He also guides you through writing your own cards! Credit card scammers - the reader/writer won't write to hi-co (high-coercivity) cards, so you won't be able to go and make a duplicate of someone's credit card. Sorry! For all you legitimate hackers out there, this is a cool technology to play around with! Have fun!