This is a great way to quickly and informally assess students during small group or individual instruction -- students write a statement in response to what they have read, discussed, or learned, as well as a question. (use post it notes)
They sell these tins at craft stores in the wedding section (use a coupon to get a good deal) attach strong magnets. I got a metal board from Ikea and they just magnet on there. You could also paint a cookie sheet any color you like and use that.