I am looking to duplicate functionality of a site I frequently use to purchase my own organic food and vitamins (http://www.iherb.com) whereby for users on the first order, they receive $5 off along with free shipping.
If you enter the coupon code: GOV193 you get the $5 off. Likewise, you can generate future discounts based on the code assigned to you at checkout when you share with others. Looking for shopping carts that have already implemented this function.