Can you make resistors out of ice? :-)
I think I read somewhere (this may well have been on Usenet) that
somebody had 'doped' ice with suitable ionic substances and made very
crude transistors from it :-) A frequency response of 1Hz was good IIRC
(the charge carrier mobility was darn low...)
Lack of power on the parallel port's a strange one - I always found it hard to
believe that the implementors didn't forsee the use of the port as a
general-purpose output port and provide it with a couple of power pins. It's
not like there aren't several grounds available so that couple could have been
given up for +5V pins.
I used to power external gadgets from the PC keyboard port because I happened
to have the right connectors to hand in order to tap power from there - that
was at least portable until everywhere went to ps/2 type keyboards.
Well, PS/2 keuyboard connectors also carry a 5V line :-)...
The other place is the joystick connector (AFAIK the ones you find on
soundcards still have the 5V line available, but I don't have a soundcard
to check).
One thing that annoyed me as a circuit that needed a single bit input to
the computer. It used ome of the lines on the parallel port, but you had
to get 5V from somewhere. Why not use one of the switch inputs on the
joystick port, you can get 5V from the same connector. Of course the
software came as a binary only, so you couldn't modify it to use the
joystick port.
One of my other machines just had one of the internal
drive power connectors
fed out of the back of the case though for a useful point to take power from.
Somewhere I have a 'PC bracket' with a little PCB on that that doesn't
plug into any motherboard connector. Instead it's got a 4 pin connector
that takes a '3.5" drive power connector (if you see what I mean), from
which it takes thr 12V line). The PCB contains a 3 terminal regulator
with a jumper block to set the output to somewhere between 3V and 12V
(most useful voltages, including 5V, are catered for). The output appears
on one of those coazial power connectors, poking through a hole in the
bracket. I assume it was indended to power PC speakers or the like from
the computer power supply. It would be a lot more use to me if the
voltage-setting jumpers were accessible from outside the case :-)
-tony