I've always been interested in electronics but never really progressed beyond the gadget store 100-in-1 experimenter kit level. In fact, the last little experiment I tried as a kid nearly set fire to my workbench. It was then that I realized that computers were easier - in general, they were already assembled and typically weren't the cause of too many house fires.
So when I caught wind of the concept of physical computing (computers that an sense and respond to the outside world), I thought I'd give it another try.
One really inexpensive way to get into the hobby is the Arduino prototyping platform. It's a small microcontroller board that allows for programming code to be uploaded into its microprocessor and can be powered by USB, batteries or even alternative sources like solar power. There are a lot of add on boards (called Shields) that you can purchase and assemble to try your hand at more advanced concepts like GPS logging, sound generation and controlling servos and motors. Some of the more interesting work being done with it can be found on the official Arduino web site.
But for the moment, I'm only fooling around with the thing, getting my head wrapped around the concepts of transistors and diodes again. About the only thing I'm able to do with it right now is to get an RGB LED to cycle through all of its colors.
If you're tinkering with Arduino, I'd love to hear from you.