To quote myself:
Dispensr is a better way to distribute multiple promotional codes for iOS and Mac software. You just upload the file you receive from iTunes Connect and you get a single, private url to share via email or on Facebook, Twitter or App.net. Your users get to request a code without trying multiple times only to find out that they've all been used.
Dispensr was conceived of a week ago and built almost entirely over the recent holiday weekend. It met a need I had and I figured I might not be alone. The service is still a work in progress but it's functional and completely free. Try it, share it, and let me know what you think.