Mobile disk solutions for the iPhone have been popping up all over the place since the iPhone was announced. Using your phone as a storage device is a logical extension, that until recently involved some third party applications or a jailbreak.
Apple changed that today by releasing the MobileMe-iDisk application for their mobile line. It’s free and early indications are that you need a mobile me account to use it which is a huge missed opportunity (gDrive anyone). It would have been nice if they went the same route as the AirSharing app and allowed us to connect over a wireless connection (That would probably duplicate functionality though, and Apple would have to yank their own app! Huzzah!).
Anyway, it’s free, so if you have mobile me go check out the application.