Magnetic stripe reprogramming

[Grand_Master]

Where can I find details about magnetic stripes?

I and a friend are thinking about buying external hardware that can read/write/modify the information stored in a magnetic stripe of different cards.
I do know that I wont be able to hack banks this way. But there's a lot of different cards out there. I may be able to hack buscards and similiar.

What do you think? Do you know anything bout sequritysystems of those subjects?
I think that buscards could be pretty simple, as the busses don't make validation checks towards any kind of server.