Two years ago, Kellogs Canada had a program that you mailed in two pieces of a cereal box to receive a prepaid $5.00 gas card. Awkward, as you had to fold over a 4x6 piece of cardboard and place 2 of them into an envelop. Wait period was less than 4 weeks. It was a great deal as cereal price was about $2.50, so for $5.00 you got 2 boxes of cereal and $5.00  of gas.  Last year we had to buy 3 boxes of cereal, so it was still a good deal, but even more awkward mailing 3 pices of cardboard. Only one card per household, but we used children (with no car and different address) to get a couple more cards. ;)