I think the Arie Foundation (associated with New York University Medical Center in New York City) has been gratefully accepting donations of cards for years (and comics and other stuff like that). I don't know how many 3,000 and 5,000 count boxes I've sent up there over the last 10 years, but its tons. Their website used to have pictures of kids with the cards, and I even recognized some of mine among them, but that version of the website is gone, I think. They'd also received higher dollar value cards over the years,which they used to offer up at benefit sales.
http://www.ariefoundation.com/