Neat article about BMOW's writeup about a rewritable ROM based on work from Rob Braun and Doug Brown:

http://hackaday.com/2014/12/23/rewritable-rom-for-the-mac-plus/

And the BMOW article:

http://www.bigmessowires.com/2014/12/20/rewritable-rom-disk-for-mac-plus/