Many Kmarts are doubling coupons from 2/22-2/28/09. Not all ads for that week will show that they are doubling, so you might want to contact customer service at 1-800-KMART-4U or email customer service at: firstname.lastname@example.org. Here is a partial list for a quick check, but it's best to call or email if yours isn't listed.
Why is this such a big deal, when other stores double frequently? Because most of the time Kmart doubles coupons up to $2! That means if you have a $2 coupon, you can get $4 off!