Microcontrollers

A microcontroller is a highly integrated digital or mixed signal integrated circuit that has at least the following:
 * A microprocessor
 * Clock generation hardware
 * Memory (RAM)
 * Configurable Digital I/O pins

Typical microcontrollers require only a bare minimum of external components when used in simple applications. This can be as little as a bypass capacitor (for power conditioning) and power connections, but normally includes either a crystal or a ceramic resonator (to provide an accurate clock signal) and some kind of reset logic. Most devices have on-board program storage - usually flash memory, EPROM or EEPROM.

Applications
Microcontrollers are designed to be wired directly (embedded) into other devices - normally being used to control device operation, provide user interface functions, handle complex timing requirements or handle other tasks which either require a microprocessor or or significantly simplified by using one. They are much slower than modern general purpose computers, have far less ram, have access to vastly less storage, and are generally slow and stupid. Their main advantages are low cost (<$8.00 each - less in quantity) and specialized I/O. They are currently a mainstay of modern electronic engineering, and are found in virtually all consumer electronics, as well as white goods, personal care appliances, and kitchen gadgets.

Specialized I/O
Part of the reason (aside from low cost) that microcontrollers dominate the embedded market is their support for specialized I/O. It is very common (almost the norm) for these devices to have one or more of the following:
 * Analog to Digital Converters (ADC)
 * Pulse Width Modulation (PWM) - sometimes as specialty H-bridge control circuits
 * Pulse counters
 * Comparators
 * Programmable interval timers
 * I2C ports (Inter-Integrated Circuit ports - a specialized serial port)
 * 1-wire ports (Another specialized serial port)
 * CAN bus (Yet another specialized serial port)
 * SPI ports (Notice a pattern yet? Yet one more specialized serial port)
 * Asynchronous Serial (RS-232 at TTL voltage levels) ports (What most people think of when you say serial port)
 * USB Ports

How this applies to Teledildonics
Okay, you're thinking, enough with the Wikipedia stuff already - How does this apply to SEX?

In a nutshell:
 * 1) Most sex toys are basically motors with attached to them
 * 2) The rest either need to be motorized to be useful for teledildonics or are already controlled by something like a potentiometer (variable resistor)
 * 3) General purpose PCs are lousy at doing digital and analog control work. This is because they were designed to do something else
 * 4) Microcontrollers are really good at digital and analog control work - that's what they were designed for.
 * 5) It's easy to get a microcontroller to communicate with a general purpose PC
 * 6) It's easy to get a microcontroller to do the low-level control work for teledildonics. They can even control digital potentiometers for those times when a variable resistor is the right answer to a control problem.
 * 7) Sticking a microcontroller between the PC and whatever it is you want to control makes life way easier.
 * 8) Life's too short to do things the hard way when there's a better, cheaper and simpler answer.

Buying Microcontrollers
Popular microcontroller manufacturers are Microchip Technologies, Atmel and Parallax. These manufacturers make the chips/modules that dominate the hobbyist part of the market. While the 8051 microcontroller is extremely popular in the commercial sector, the tools are more expensive, and it's not generally recommended for hobbyist and small-scale production work.

Links to both the manufacturers and major distributors may be found at PartsSources

Resources

 * Pic List - Discussion forum for PIC developers - Good Resource for examples and technical help
 * A basic book about Microchip (PIC) assembly language - Free to read online.
 * Substantial list of PIC resources from Dontronics
 * Tiny PIC boot Loader - This can save much time when doing development
 * A PIC microcontroller tutorial which does a pretty good job covering the basics
 * WinPicProg - A windows programming program for PIC microcontrollers. Also - a nice PIC tutorial