EDIT: This freebie is no longer available.
During Labor Day Weekend (9/5 – 9/7), pick up any Blue Bunny Aspen or Sedona Frozen Yogurt Granola Novelty (13 syllables in that product's name!) and then use this rebate form to make it free! They held a similar offer back in May and I received my check around a month later, so I'll certainly participate again this time. Although it really doesn't take much to get me on board for something. You could stick a sign on the sidewalk that said “go wait here” with an arrow pointing towards a dark alley and I'd stand around for an hour before I realized it was a hoax.
You have to postmark the claim by 9/19 and make sure you include your original receipt and UPC bar codes.