ive just recently watched the pcb etching episode and thought why not mod a laser jet printer to print pcb etching straight to the copper instead of transferring with an iron. ive also had ideas on how to make multiple layered pcbs. using such printed cards you could print multiple cards on one sheet then using a cnc router to cut them to the exact shape consistently for mass produced projects or to layer them. with the printer you could even apply a decent solder mask over the printed cards after etching. id love some feed back from the community too