The port on the bottom of the SL-6000 is different than the port on the docking station.
The dock has a USB mini B socket for use with the cable that came with the Zaurus.
On the bottom of the SL-6000 is a USB mini A socket for USB host capabilities. You can hook USB storage devices, USB keyboards, and assorted other USB devices to this port . To do so, you will most likely need to get an adapter.
You can find some information about the adapter in this thread:
USB Host Adapter, truly worthy of new thread!!!!!