One possibility: The grocery store seeds the site with product data from their suppliers, and customers vote up what they want to see on the shelves. New produ

One possibility: The grocery store seeds the site with product data from their suppliers, and customers vote up what they want to see on the shelves. New product lines could be "featured" weekly, and the ones that pass a certain vote threshold get ordered. If a product you voted for gets added, perhaps you get an email with a coupon.