I just saw this contraption on a colleagues desk. As you can see, a 3.5" HDD is literally plugged into the dock as if it were some super-sized memory card . Well, thats exactly what it is. The dock also has ports for USB keys, SD cards, and probably a few other formats.
Interesting to see the form factor difference between the SD slot and the 3.5" HDD slot. Flash memory capacity is quickly catching up with HDD capacity (the latter's lead has shrunk to only about ~10x). HDDs are endangered species!