I started playing around with 3D drawing nearly ten years ago using the SketchUp program when it still belonged to Google. I devoted about a year to learning the program and produced quite a few 3D models, some of which can be viewed by clicking the link to my 3D Warehouse folder over in the right column.
(Left click for 3D interaction. Model loads slowly. Hold down center mouse button to drag and move model.)
Trimble, Inc. took over the program and made quite a few additions and improvements to it. Now, they have made an on line beta version available. It is surprisingly responsive, and fun to play with.