Ok, so say you are in the desert, have no computer in sight, but for some strange reason there is an amazing wi-fi connection. You just got a promo code of some game you really want to play. BUT THERE IS NO COMPUTER REMEMBER, HOW DO YOU GET THE APP!?!?!? Here's how. Open up your iTunes Music Store App (NOT APPSTORE) and go over to downloads, then click redeem in the top left corner. Enter the code, and it will pop up saying thank you, blah blah blah, and there will be a picture of the app. It also tells you it will download the next time you are on your computer. OK, so exit out of that, enter the app store, and viola!! Your app will start downloading immediately, hit the home button and watch it install. Well, there you go.
i knew about this too and posted about this on ipod touch fans forum like 2 days ago! its pretty usefull