FreeCAD - 2D / 3D
File Support:
Pros:
Cons:
Runs on:
I use it for both printing and on my router. Works great. The drawing tools are a little different than other 2D programs (AutoCAD, LibreCAD) but there are a lot of tutorials available and once you learn how to use it, it is very good. Some of the tool paths still need some work as curved surfaces in pockets don't always seem to give the desired results.
Working with parts and 3d primitives is quite easy.
Overall I like it and the cost is just time.
I personally have used a cool feature in the FreeCAD software that allows you to convert STL meshes back into a solid more manipulation. This little shortcut of taking an STL and making it into, say, a STEP file gets more complicated the more triangles you have in the STL since each triangle face becomes a solid face afterwards. But nonetheless, it works great for smaller, less complex STLs.
I've used FreeCAD plugins as well to generate gears.
FreeCAD was also my source of learning how to 3D draw before I moved onto Fusion360 and Inventor. All in all, FreeCAD is a great free open source software.
I agree, FreeCAD's STL to solid conversion is a very handy tool to have. Here's a tutorial on how to do it. It has lots of step by step pictures!

https://www.youtube.com/watch?annotation_id=annotation_1342499087&feature=iv&index=1&list=PL1P4z1vfrsq8KZ2mHqRBZg8aoftq_w6vY&src_vid=SPFoXfEAufw&v=SCPF2ob3p1Y
good french tutos
tutoriels en français
For French tutorials; Copy paste the link in your browser:
https://www.youtube.com/watch?annotation_id=annotation_1342499087&feature=iv&index=1&list=PL1P4z1vfrsq8KZ2mHqRBZg8aoftq_w6vY&src_vid=SPFoXfEAufw&v=SCPF2ob3p1Y
FreeCAD can use two external rendering software in the Raytracing workbench, LuxCoreRender and POVRay. I haven't found either of them to be fabulous rendering software when it comes to ease of use but they do get some jobs done fast.
The two external rendering software options can be discussed at the below links:
POVRay:
https://grabcad.com/groups/free-cad-cam-software-options/discussions/povray-rendering
LuxCoreRender:
https://grabcad.com/groups/free-cad-cam-software-options/discussions/luxcorerender-rendering
I do my FreeCAD-model-rendering lately with CADRays. Not very sophisticated but delivers immediate results.
FreeCAD also has a Spreadsheet workbench that can be used to keep track of information as well as drive CAD dimensions. Very helpful if you keep changing only one or two dimensions on a part and all the rest stays the same from model to model.
FreeCAD has an addon workbench for working with assemblies called A2plus. It can be installed from the addon manager inside FreeCAD or can be found here:
https://github.com/kbwbe/A2plus
FreeCAD documentation:
https://wiki.freecadweb.org/A2plus_Workbench
FreeCAD has a noinstall portable version available on their site for download now