Check out the Megaprocessor[0]. A guy made his own "processor" out of roughly a hundred thousand transistors, resistors, etc. Really interesting project.
So impressive, but I am so happy to never have any reason to need to do anything like this myself. I used to fix IBM mainframes like 3033s back in the day, and debugging computers made up of gajillions of interconnected frames, boards and cards, under immense pressure, was truly the stuff of nightmares. After hours or even days, victory was finding a ringing signal with your scope, caused by a loose trilead. Then you went home and slept for a day.
The rusty razorblade + pin point contact diode doesn't need anything special because it's a Schottky diode, with a metal/N-type semiconductor junction. If you probe lots of places you can find an N-type region where the dopant is random impurities. But the transistor needs both N and P-type regions, so I don't see any way to build one with common junk. Jeri's point contact example works by diffusing phosphorus from phosphor bronze into commercially produced N-type germanium using a high current to heat it. Phosphor bronze is arguably household junk but I don't think germanium diodes are.
