Microcontrollers are chips that have almost a complete digital computer system on board. To use them, you just hook them up to whatever machine you want to control (whether a coffee machine or a space satellite), write a program that makes it do what it should, load the program into the microcontroller, and turn on the power. Billions of microcontrollers are made each year, by about a dozen manufacturers and based on just a handful of processor architectures.

• Dallas Semiconductors DS80C400
  Based on the humble 8051 core, but loaded with a huge arsenal of peripherals. Made by Dallas (now Maxim).
• Atmel ATtiny45
  A small, 8-pin chip from Atmel's popular AVR series.
• Hitachi HD64180
  Found inside an anonymized chip powering an old piece of network equipment.