As they do every year, Autodesk are giving away their latest version of AutoCAD® for free. The download link is at the bottom of this page.
It’s free for a limited period of time though – 30 days. Still, this is more than enough time to get some basic work done or evaluate the software for future projects. Be careful modifying existing drawings – I do remember one occasion when I edited some vital drawings with a trial version and saved them, thinking nothing of it… only to find that I’d saved them in a new file format. When the trial duly expired, I was then stuck with no way to open the files!