The offer listings sections in the Marketing tree lists out all your 'Offers'. Which are in effect discounts you want to offer customers.
The concept of an offer is an abstraction that developers can use to implement different sorts of discounts as well as conceptually other types of "offers."
Included in the Merchello.Core we've included a Coupon Provider - "Coupons" and a new Coupon Editor page which should allow editors to create quite a few different types of coupon offers. The system is based off a single reward (like % off or FREE shipping) that can be optionally constrained by one or more constraints APPLIED IN A CONFIGURABLE ORDER.
It is conceptually a complicated system, but it is extremely flexible.
Both rewards and constraints are resolvable, so if you do not find what you are looking for, you can roll your own. If this is something you are interested in trying, checkout the classes we've included in Merchello located in the Merchello.Web.Discounts.Coupons namespace.
Updated less than a minute ago