Current Status - Working out specifications.
So, we want to make a machine for 3d printing, cnc drilling, pcb routing... They have a common starting point, an X-Y gantry.
First thing we need to decide is what size we should make it.
My thoughts, for a first testbed, are to make something fairly small, bed size of about 200mm x 200mm. This can then be driven from a few stepper motors (we have some lying about from murdered printers), using either a belt drive or threaded rod ( would be perfect).
Once we have this running, we can use a dremel for the router bit, and have a working small CNC machine, that can be used for PCBs and making small parts from foam and wood. I'm looking at  for guidance, which is an instructable written by oomlout, seems like it'd be a good place to start.