Years ago, when I first got started with 3D printing, a friend of mine Kristoffer Syversen (GitHub, LinkedIn) mentioned OpenSCAD passing in conversation. I don't really remember what he said, but I remember that he sounded pretty excited about it.
Now I get it. I have no idea what took me so long to spend 2 minutes looking up a code example, but boy did I have the wrong idea. I thought it would be complicated and burdensome (being half-decent at Blender, having learned Solidworks in school, and played around with FreeCAD). Since my faulty assumption has now been corrected, OpenSCAD will likely be my favorite tool for most things CAD in the future. After having spent 20 minutes I'm already more productive than in FreeCAD or Solidworks. The fact that everything is human-readable code makes things a lot easier to maintain, encourages reuse, and makes it work great with version control.
So, here I'll dump what I got. Enjoy, I hope you find OpenSCAD as fulfilling as me.
Just download OpenSCAD. On Linux systems you are likely to find it in your package manager.
In the future I might set up generation of STL files to a static site (which can be previewed in browser).