Some free drafting and design applications are Google SketchUp, DraftSight and DraftIt. These are all completely free and offer excellent design tools as of 2015. Google SketchUp, previously called Trimble, is one of the most popular design tools ever available for free. It features a simple 3-D design interface that is relatively user-friendly. SketchUp can be used quickly to prepare designs for a presentation or for more in-depth usage with accurate sizing and other features.
DraftSight is a completely free software package that is ideal for individual use. The only requirement for using the software is provide a valid email for activation. It is very similar to AutoCAD, the standard tool in the field. The included features are all that users need to create professional plans.
The free version of DraftIt is a little more stripped down than DraftSight and SketchUp. It likely isn't a good choice for anyone trying to do regular or serious design work; however, it is ideal for anyone who is learning about using drafting and design software.
Other free options include AutoCAD Student Version, which is the full version of AutoCAD available for free to students. Furthermore, Rhino offers a free, full-feature trial as of 2015.