If you're looking for basic CAD software packages and don't need highly technical functionality, you'll likely find everything you need, and maybe more, in one of these free CAD programs.

FreeCAD is a serious open source offering that supports parametric 3D modeling, meaning you can modify your design by going back to your model history and changing its parameters. Its target audience is mainly mechanical engineers and product designers, but it has a lot of functionality and power that anyone would find appealing.

Like many open source products, it has a loyal developer base and can compete with some commercial heavyweights due to its ability to create true 3D solids, support for meshes, 2D drawing and many other features.

Furthermore, it is customizable and available on multiple platforms including Windows, Mac, and various Linux distributions such as Ubuntu and Fedora.