Hi all,
A while ago added an Arduino with some Sparkfun relay control boards to an Ikea childrens traffic light lamp, to use as a software project status indicator, attached to my office build server. They've been working in production for several months now and are a really useful addition to our office. It was my first microcontroller project and was amazed at all the information and resources available to do such things.
Here are a couple of pictures, and you can see more (including a video and all the code) on my blog at www.fixmybugs.com.
Cheers,
Steve