Buy One, Get One at a Discount?

[fright-rags]

I was wondering if there was a module available that would let me set up promotions based on the product ordered. For instance, I would like to be able to tell a customer that if they buy one of my shirts, they can have another shirt at 15% off. So I would set up the "super product" in the admin (the qualifying product that must be in the cart to activate the discount), and then choose which products or categories that are eligible for the discount when they add them tot he cart (along with the super product). Is there anything like this available?

[swguy]

Look at Better Together in the downloads area.