The best microcontroller trainer

Well, it all depends on your level of programming experience, if any, and your level of electronics experience, if any. If you're an absolute rookie in both, then I would say start with the "Basic Stamp Activity Kit" from Parallax. This will get you started pretty quickly, give you a good idea of what a microcontroller is and what you can do with it. After that you will need something a bit bigger. I like the Atmel STK-500, it can handle most of the Atmel line of microcontrollers and is easy to connect to the outside world.

If you're completely lost, like wondering just what a microcontroller is to begin with, read on, or else skip this part. A microcontroller is basically a very small computer used to control things like motors or LCD displays or even just little lamps in response to signals from outside, for example, controlling two motors on a wheeled robot with input from photocells or bumper switches to determine what to do with the motors.

Give us some idea of what you're into, what you would like to control, and how much experience you have in electronics and programming and we'll be able to tell you more.