Google SketchUp
Tutotials - Few tutorial videos on basic google SketchUp.
STL Extension Install - Youtube video on how to export STL file form sketchup
SketchUp to STL - Here you can download the extension for sketchup in order to export your drawing in STL format for 3D printing
SketchUp download - Here is the link where you can download google sketchup for free
Makerbot software download - Download makerbot software for free in order to 3D print your parts