Since the iPad doesn't have a USB port or SSD card slot (can I say "grrrr!' again?) Apple sells a Camera Kit that's supposed to let you plug in your camera or card and transfer your pictures and video -- but also used to work for low power USB keyboards and Skype/VoIP headsets. I say "used to" because with iOS 4.2 that no longer seems to be the case.
Mark Gurman from 9to5mac has done some tests: