Full sized memory foam mattress for $180 after 10% sale and 10% off for "new customers".
Go to overstock.com/coupons and click the coupon, it will automatically be applied in your cart. Free shipping because it's over $50.
4.6 rating after >200 reviews. After, ahem, a few hours searching for a good memory foam mattress for a low price, this really seems to be the best deal.