I save Box Tops for my friend's daughter, since our school doesn't collect them. I bought an inexpensive magnetic spice canister to put them in. It has a slit on top, making it easy to drop them in. The window on the front makes it easy to see how many are inside and everyone in the house knows where to put them. It is hung in plain sight, so it also reminds me to look for Box Tops on items when I take them our of the refrigerator.
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Did you know these are worth cash to non-for-profits? Save them and ask around. These are collected by Girl Scouts, Boy Scouts, 4H kids, youth groups, schools, missionaries, and more. Ask around and you will find someone who will take them.