Here's a fun family activity for a rainy day: Voice drawing. ZeFrank.com has posted a beta voice-controlled drawing tool that taps into your computer's microphone to allow you to draw using the modulation of your voice. It's sort of like a sound-based virtual Etch-a-Sketch.
Ze says that a sound at low volume creates a counterclockwise curve, a medium volume sound creates a straight line, and a high volume sound curves clockwise. The images in the gallery are of faces Ze created using his Voice Draw tool.