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.

My programming is weak but I'm not bad as far as electronics goes. I guess
I'll go with a toy to build up a little programming experience. Thanks.