The following information comes from a Nintendo Power interview with Eiji Aonuma...

“I really think [having two screens is] one of the most exciting features of the system. Unlike the Nintendo DS, there’s distance between the television and you and your other screen. That really allows for some different interactions, some of which you saw [at E3]. For example, imagine having the contents of Link’s satchel available to you on the screen of your controller, and using elements of the pouch to interact with gameplay on the television.

With The Legend of Zelda: Skyward Sword, we had the Nunchuck and Wii Remote sort of stand in for the sword and shield that Link carries. But in a game for the Wii U, I can definitely see something like the controller itself becoming the different items that Link is using, allowing you to interact with the game world and with the game items in a very different way.” - Eiji Aonuma

Please, Aonuma...PLEASE don't get me hyped up for Zelda Wii U before Skyward Sword is out the door. I'm about to explode waiting for Skyward Sword...I don't have enough in me to already start wishing for the entry after that!