shop.iseecards.com you can use the promo code mathisfun for 50% off anything up until April 7. You can give this code to as many people that you want.
I am not affiliated with this company. I just thought ti was a nice offer from what appears to be a family run business.
They did a promotion and sent us (and many many other people) a free deck. I recieved the pyramath and it was simple and versatile. It comes with directions but you could easily make the game go any other creative way.
I am not sure about the other decks.