Owners of Makerbot 3d printers have discovered that adding BlinkM MaxMs their 3d printer is easy to do and gives their bot an extra cool feel. This excellent mood lighting system by jetty is one of many examples of how to do this. Other users are using MaxMs to indicate bot build status. All you need is a BlinkM MaxM and some LED strip, both available in the Makerbot store.
(image from gizmag.com)
If you're curious about BlinkM MaxMs, here's some more information.