Electronics Learning Lab
This week I visited a second-hand store (Value Village), and found a RadioShack Electronics Learning Lab for $7 (USD).
RadioShack Electronics Learning Lab (Angled View)
RadioShack Electronics Learning Lab (Top View)
I'm giving it to my oldest son as a present. He was very excited to start using it, but we ran into a difficulty as there was no power transfer between the battery pack and the breadboard power bars. I figured out that, aside from some corrosion on the battery-holding coils, one of the coils was compressed in and not making contact. I pulled that out and now power transfer is working fine.
The unit has 3 potentiometers, 4 push-button switches, a DPDT switch, a transformer, a relay, a buzzer, a speaker, a photoresistor, an ammeter, 10 LEDs, and an 8-segment display.
My four-year-old is pretty smart, but I'll have to monitor him and teach him, to make sure he doesn't make a short. He already tried out the buttons, LEDs, and the photoresistor.
For posterity, here is a picture of the inside of the case:
RadioShack Electronics Learning Lab (Inside)