The documentation for the plug talks about a cable with a normal size "A" end and the mini "B" . Which end fits the plug computer.
The SheevaPlug has a normal USB "A" socket and a USB B "miniport" socket.
The reason I am confused is because the documentation seems to imply that to use a serial console, you drive it through a usb port of another computer, yet there is also discussion of plugging in standard usb memory sticks into the usb port.
The serial console is accessed connecting your desktop PC via the supplied USB "A" to miniport cable.
Additionally, the USB "A" socket of the SheevaPlug can be used for devices such as memory sticks or wireless cards. We hope eventually to be able to provide a list of devices that we have tested, but thus far we haven't had enough time to test more than a handful of memory stick.

Does this help answer your question? In the image above you can see, from left to right, (1) the ethernet port, (2) USB socket, (3) miniport, and (4) SD card slot.