A lot of Asus tablets have an optional keyboard that has a single USB port on them. The keyboard also doubles as a secondary battery for your tablet, which really makes it worth having. The tablet and docking keyboard, when together are very very much like an extremely slim touch screen netbook. They go together very seamlessly and are not flimsy in the least.
The only caveat is that you can only have ONE usb device on the unit. Android does not support usb hubs (as far as i've been able to see) so you cannot plug in your camera, and the external drive and transfer files. This means that if you have a camera that is using compact flash cards, you'll have to first upload the photos to the unit, then to the External drive. However, if your camera uses SD cards, then you can pop the card into the keyboard (it has an SD slot also) and the external into the usb port and happily transfer any file you like.
Benefits to the Asus transformer series:
Micro SD port
SD port
USB port
15 hour consistent use battery life (I mean that too, you can watch movies or cruise the net for 15 hours + on a single charge with the keyboard attached, I've done it many many times in airports around the world)
mechanical QWERTY keyboard with touchpad mouse
Touch screen
Android mobile operating system.
I have two of these things, and while I don't use them to upload my images, they are extremely useful in many other ways.