Sometimes having the right tools can make all the difference in the world. A lot of really good software packages can tend to be “best kept secrets”.
This is a list1) of software that Maker may find useful. Everything on this list is “free” (“gratis”), “free” (“libre”), or at the very least has a “light” version for non-commercial use. (Some may restrict commercial application, or require a paid license to use commercially, always check the license ahead of time, and compensate engineers for their work when they ask for it). Applications that are “trial” versions in that critical core functionality is fundamentally crippled or time limited are ineligible for this list.
Anibit staff tends to lean toward Microsoft Windows Desktops, and so this list may have somewhat of a bias, but many of the listed software is cross-platform, and we'll try to make a note of additional platform availability. In addition, many Mac and Linux user are likely already aware of many of these applications.
And now, on to the list…
Libre Office is an open source cross platform office suite.
Libre Office is a fork of the Open Office project. If you haven't tried Libre Office or Open Office in a while you should really give this a try. The quality and compatibility with Microsoft Office has improved a lot in the past couple years.
A graphical file archive management tool, reads many formats. Can create zip files.
The Gimp is the defacto standard in open source full-featured graphics editing applications.
The Gimp has been around forever, and is quite mature. The Gimp supports multilayer images, exports and imports many 2D raster formats, and comes with a multitude filters and plug-ins.
A mature, full featured 2D vector graphics editing tool focused on the SVG vector graphics format.
FreeCad is a Parametric CAD system/Parametric model. Despite its disclaimers that it might not be ready for production use. I have found it very stable and reliable. It can read and write a variety of 3D and 2D CAD formats. The “parametric” aspect of it lets you get really sophisticated with the editing workflow. If you are familiar with Blender 3D, it is similar conceptually to using it's modifier stack.