Like managing inputs and outputs for unplanned results? Here's a bit of background on what Arduino is from the Make Magazine Archive

Arduino is a tool for making computers that can sense and control more of the physical world than your desktop computer. It's an open- source physical computing platform based on a simple microcontroller board, and a development environment for writing software for the board. Arduino can be used to develop interactive objects, taking inputs from a variety of switches or sensors, and controlling a variety of lights, motors, and other physical outputs. Arduino projects can be stand-alone, or they can be communicate with software running on your computer (e.g. Flash, Processing, MaxMSP.) The boards can be assembled by hand or purchased preassembled; the open-source IDE can be downloaded for free.

I'm just getting started with this new high-tech electronic tinkering, but got the book from Amazon yesterday - with this one soon to be ordered]- and am getting some hardware by the end of the week to start my forays into embedded computing. I have a ton of ideas for what I'd like to do with these, including little wireless networking fun with Xbee. Stay tuned to see what's happening here. It's going to be big.