How do you use your iPhone as a usb key? I saw a friend of mine manage to use his iPhone as a usb key. I had a large file that I needed to transfer to his computer. So he gave me his iPhone cable, had me open iTunes, open his iPhone in iTunes, select some app that was on his iPhone, drag and drop my file there, and then he could get the file to his machine.

Which app was he using? I want it, too!
I haven't tried it yet, but from this description, it looks like Air Sharing is what I want.