$1/2 Special K Target Web coupon, so stack 2 of those with 2 B1G1, and you will get 4 boxes for $3!!! (Target's coupon policy allows you to stack a manf. coupon with a target coupon on the same item)
If you go to the Special K website and "design a plan", you will be able to print off a B1G1 coupon (hit your browser's button to print it twice). Special K is on sale 4/$10 at Target this week, bringing your total down to $5 for 4 boxes of cereal!!! Fantastic deal!
Don't forget, you can create a free email account to use specifically for coupons and deals, so you don't get all the extra mail mixed into your normal email account! I personally use gmail, which has very little spam and is very simple to use.