How to prepare Mesh for 3D Printing

Blender3D
https://www.blender.org

MeshLab – open source, portable, and extensible system for the processing and editing of unstructured 3D triangular meshes
http://meshlab.sourceforge.net

netfabb – Software for 3D Printing
http://www.netfabb.com

3D printing tutorials
http://3dprintingforbeginners.com