From July 1-24, 2016, you can download your free Shaymin (land form) in Pokemon XY/ORAS through Mystery Gift > Get Via Internet! No code card required! Want the sky form of Shaymin? Take it to Route 123 in ORAS to receive the Gracidea flower, which will change Shaymin’s form!
As always, for more information, you can check out the official webpage. Good hunting, trainers!
While you’re at it, don’t forget to pick up a Generations Trainer Box!