And now for something completely different - using Don Sauer's detailed instructions you can make your own curve tracer. It is made possible with some interesting external analogue circuitry, and Processing on a host PC to work with the data from the Arduino board. The purpose of this is to analyse characteristics of transistors such as the collector current as the voltage changes. The circuit is relatively simple, and Don has documented it very well.
To get started with your own Arduino-embedded projects, look no further than the Freetronics LeoStick. Apart from being one of the smallest Arduino-compatibles on the market with USB, it also has an onboard RGB LED and piezo for sound and knock detection: