[Jamie Zawinski] explains how to build an useful tool to automate the curtains with Arduino.
I built a controller so that I can open and close my curtains from the command line! My apartment has a 16' wide floor-to-ceiling window, and a correspondingly-huge curtain. I wanted to put the curtain under software control so I could do things like, for example, have it automatically open in the morning to help me get out of bed.
Via and source: JWZ