When I played around with 3d printers a number of years back, I tried a few free programs such as Blender, FreeCAD and Sketchup, but I found OpenSCAD for modeling and Meshlab for post-processing to be the best pipeline for my needs.
OpenSCAD is particularly effective for making replacement parts where precision is more important than aesthetics.
However I did find ways to have fun with it, such as building a printable dragon fractal: https://s3.amazonaws.com/www.subalpinetech.com/images/dragon...https://s3.amazonaws.com/www.subalpinetech.com/images/dragon...
