One the coolest open source projects out there is the Arduino. It's an open-source electronics platform based on a Amtel microcontroller. This is one of the cooler and more practical Arduino projects I've seen so far. It's a simple oscilliscope (10 bit resolution), but it will only set you back $30 bucks. (Hat tip to Hacked Gadgets.)
Poor Man's Oscilloscope (Arduino + Processing)
BTW, if you are not familar with the Arduino. There's a great podcast with the projects founder about Arduino at FLOSS Weekly.
