Seth Godin made a wishlist of iPad app and readers of his blog created them. One them is nonlineair: "it lets you import a PDF or PPT file and then jump around. It's not for building slides, it's for navigating them, and even includes a way to drive an external monitor in a clever way." It is available or $10 in the app store, $2 of which will go to the Acumen Fund. I still need to find time to review it.