I just got word that K-Mart will be doing Super Double coupons again from this Sunday, Oct. 26 through Nov. 1. They are doubling all coupons up to and including $2 coupons (so a $2 coupon would actually be worth $4), so this is a great way to get lots of free or nearly free items to donate! For a list of coupon match-ups visit Hot Coupon World.
EDIT: To see if your store is participating, go to this link at Hot Coupon World and look at the third post on that page. It's a pretty comprehensive list.