A lot of press just prior to the iPad shipping was around OmniGraffle for the iPad. A solution that works better with your finger than a mouse, a natural for the iPad. A bit of the press was around it being almost 50 dollars, but that just makes it a Business app and not something you buy to ‘play’ with.
If your a OmniGraffle Desktop user, you may enjoy a new Free Template (Stencil) of iPad screens, keyboards and buttons. Great if you layout out a iPad app’s user screens, workflow or concept presentation.