FreeCAD is, you guessed it, free. That's not the best thing about it, though. With a range of parametric 2D and 3D tools, FreeCAD makes it easy to generate results quickly and efficiently. The software is only let down by its basic interface that is far from intuitive, especially for beginners. Having said that, if you only need a CAD application now and then and don't need any advanced features, then FreeCAD is the best solution by far.