I haven't seen any websites for used equipment yet. Some Ceramics supply
places have a bulletin board where they will post information about classes
and used equipment though. They are good places to look for people who
are selling their used equipment. Do you have any supply houses near you?
You could also try bulletin boards at junior colleges and university art
Another good source for information about clay and clay related questions
is the list serve for clay artists.
It is called: CLAYART