Has anyone tried extruding onto fabric? Is the extrusion liquid enough to seep into and bind securely with a fabric material at the extruder tip?
If so, this opens up some possibilities :
A RepRap T-Shirt with a 3d plastic printed logo.
(Later on) T-shirts with electronics printed directly on. You can get a geeky t-short with a wireless network detector, butit's basically a plastic box with electronics attached to the short. Simple LED circuits might be possible, or printing an attachement clip for your own rep-rapped box
Also, you could use fabric as a base material, leaving it attached. Extrude onto the back side of velvet and trim off the excess when finished. This would leave one side with a fabric finish - like a paperweight, or to provide a soft covering for 'feet'.
If if sticks, but is only semi-permanent, it could potentially be used as a bed material. The flexibility might help to allow a little bit of shrinkage or curl without detaching the object, allowing it to stick where otherwise it would detach. it might be easier to peel off a fabric rather than detach from a board.
Of course, I might be barking up the wrong tree - until I've built my own reprap, I can't test it...
:-)