Sketchup

You can download this program for free for mac or pc from your G-mail (Drive/More/Even More)
Best to just start the program and work your way through the videos.

Beginning Tutorial Video
http://youtu.be/oyXOng0nxS4


Tutorials (The first one is "3D Escher Tilings with Sketchup")
http://www.youtube.com/user/bonnieroskes


Tutorial on Sketchup
Guitar foot pedal
http://youtu.be/3VdkvproYIc

Tips for creating objects for 3D printing using Sketchup
http://www.mastersketchup.com/8-tips-for-3d-printing-with-sketchup/#