This is my latest add on from Zencart. This addon for Zencart allows a store owner to add a twitter has tag on the coupon admin page. Customers will need to register their twitter usernames with you store. Once this is all setup a user can tweet the Twitter hash tag, and they will be emailed the actual coupon code/offer. The Twitter hash tag can anything you set, but you would like would want something unique to your store.
This still allows all the same feature and benefits of standard coupons in Zencart. You can still set the minimum order, expiration date, and number of redemptions. Anytime a user has been emailed the coupon for the Twitter hash tag, Zencart will log it, so a user will only get emailed once. This also allows for the possibility to see who has tweeted which hashtags, and when.