Most people just throw it away when they don't need it anymore. But other use the small credit card size card as a canvas for art, origami and other art-like inspirations.
remember lots of advertisers and local tourist stops using the backs of the cards for messages and promotions. But, others have used this little 3x2 card as a canvas for paintings and silk screens. Or, used discarded cards to make origami-like objects.
From the Upcoming ueue, submitted by Baierman.