Continuing the development of the Menger sponge models, and encouraged bymathgrrl, this OpenSCAD script combines the cut and external support options and adds the ability to change the size and choose the order/level up to 3. 
Feb 6 update - added two more capabilities to the script: 
* a combination of cut and supported, to print a half-cube with the cut side facing up for folks with difficulty removing the finished object from their printbeds, 
* an option for an order zero cube - just a plain cube, no holes - so you can make a set showing the progression from cube to fractal.