Arduino
Arduino is a open-source i/o board. It talks to your computer via USB or serial and has a few digital and analog inputs and outputs. Ever since pete started thinking about using a microphone input of his laptop for reading voltmeters I have been searching for ways of "automating" experiments in my Labs. This seems promising. Most defiantly its cheap enough for me to be able to afford one and have a play with. You could also solder one yourself if you wanted to.
Does anyone know how fast a "normal" oscilloscope samples its inputs? How fast can the Arduino read one analog input and send it via the serial link? Maybe it is too slow to function as a oscilloscope. Especially when you start using it to set analog/digital outputs.
In the specs of the micro-controller on the Ardunio it says 13-260mus conversion time and 15kSPS at 10bit resolution.
Their list of tutorials can be found here http://www.arduino.cc/en/Tutorial/HomePage, this site could be especially interesting as it has "labs" on it, so some educators are using it and might have good ideas.
As so often, I learned about Arduino from hackdiary.