We have yet another $1/1 printable coupon for Post Shredded Wheat or Grape Nuts cereal here. If your Walgreens carries the 9.25 oz box for $1, you will be able to pick up more free boxes of cereal. Even if not, this high-value coupon should score you a nice deal with a sale.
In addition to the link above, there are some additional coupons available as well. I posted about these other ones earlier:
$1/1 Post Shredded Wheat or Grape Nuts Cereal
$1/1 Post Shredded Wheat Cereal