I checked on Snopes; this one is for real:
5-yr old Noah Biorkman is in the last stages of neuroblastoma cancer. His family is celebrating Christmas next week and all he wants are Christmas cards. Let's see how many we can get to him from all over the world very quickly–tell your friends in Japan and Papua New Guinea and South Africa and across the U.S. and beyond. I see thousands – THOUSANDS – of cards telling little Noah (and his grieving family) that in this big wide world, he matters.
1141 Fountain View Circle
South Lyon MI 48178
(Thanks to Evelyn Kalinosky for pointing me to this.)