I wrote a blog post that explains how to setup a Raspberry PI from scratch to control a USB traffic light.
http://blog.codecentric.de/en/2013/07/u ... k-devices/
Here is an example what my setup looks like.
For displaying the status of a software project I was working on with a team of developers, I bought a USB traffic light. Depending on the status of a Jenkins continuous integration job, the traffic light would change to RED, YELLOW or GREEN.
I wrote a script for controlling the USB traffic light that is connected to a Raspberry PI. You can find the project on github:
https://github.com/marcelbirkner/jenkin ... ck-devices