While not as neat looking as Voultars saturn bios replacement (looking at it makes me want to go back and tidy it up):
I've added a PIC to switch the saturn between 50/60 Hz with the reset button while still being able to reset the saturn with it.
I also did a Dreamcast bios replacement:
This is actually a botched bios replacement though since a pad was partially lifted during removal of the old bios and since the trace that broke went to a via under the chip I found a place on the back side to patch it:
Seriously though while I'd be happy to see what I've done if I opened up a modded system you guys leave me in awe. The soldering part is easy and pretty much boils down to "use enough flux" but the how some of you route the wires inside is oozing of craftsmanship for lack of a better word.