Well, here is another script that I found useful.
I have a Laser Cutter with a Leetro 6515 controller in it. The machine does not understand dxf files, but requires a proprietary .MOL file that is created using their LaserCut software. This script takes .MOL files and imports them into QCad. All vectors of the artwork should be imported. Movement with the laser off generates grey vectors. Movement with the laser on is colored from dark red (slow motion) to hello (50% speed) to white (100% speed). The coloring makes the acceleration curves visible and helped understanding the file format.
What is this good for? Well, I use it for testing my .MOL file generator, but it can also be helpful to recover a lost file that may still be in the laser cutter memory. And even if you do not have a laser cutter at all, this script may be a useful base for importing binary files into QCad using only Qt Script.
Oh, and since the format is proprietary and undocumented, there may be bugs when importing.