For quite some time I was trying to find an easy way to print etch-resist directly on copper-cladded bare PCB from Gerber files.
The natural approach would be to use 3D printer, to deposit etch-resist... the only thing really needed for the task is Gerber -> G-CODE converter.
This webpage suggests it should be possible to do exactly that with RepRap Host (it should convert gerbers to g-code via Skeinforge slicer.. but all my attempts to load Gerber into RepRap (Java version) were unsuccessful.
Another possibility seems to be ACE 3000 Translator.. waiting now for trial license.