DS likes the little book for them, and it stands up on his dresser. The Happiest Celebration on Earth version we got at WDW holds 36 pennies and 6 quarters. We only did pennies, but I think he came home with about 30.
He's into them around here now, too, so we've finished filling it up, and I expect he'll keep collecting them. Does anyone know if the regular Disney stores carry the books, or where to get plain books or other sorts of frames for them?