they are little 'boxtops for education' postage stamp thingys that you find on the labels of food that you may purchase at your Grocery store
few examples:
go gurts
Old El Paso refried beans
Specially marked Cereal tops
Betty crocker ready to spread frosting
Cambells soups cans
Pepperidge farms item
popsecret popcorn
Bic pens
spagettios
V-8
Prego
Swanson foods
Here's a link for the list of participating items:
http://www.boxtops4education.com/Image.aspx?id=3878