UPDATE 10/3/2014: I have reuploaded the scad file so that it is now compatible with thingiverses customizer.
Made this for an 8 channel relay module extension board a while ago that was just sitting naked in a lunch ware container. Note this design does not include screw hole, I was too lazy.
This design has an IO port for the digital pins you need to connect to, as well as the ports cut out for the relay connections.
I have mine hooked to a raspberry pi and switching mains voltage for simple home automation stuff.
The scad file I uploaded has all the variable available in case you need to move the windows around or want to change the shell depth or just need to adjust things for tolerance.
This is the board bought: http://www.dx.com/p/8-channel-relay-module-extension-board-for-arduino-avr-arm-51-141670
I have also added the scad script for this part, but it relies on the Round Corners Tutorial scad file by http://www.thingiverse.com/WilliamAAdams/about and can be found in the derived from section.
But his files is also a derivative from http://www.thingiverse.com/WarrantyVoider/designs who made the original library file. That is also in the derived from section.