These applications are suited for beginner 3D modelers. Articles taken from Shapeways, if you interest on software that are commercial use just visit the sites

Autodesk 123D Design
Easy-to-use yet powerful modeling tool with library of existing components or the ability to create from scratch. Also available for the iPad. Integrated and prints directly to Shapeways.
Easy-to-use yet powerful modeling tool with library of existing components or the ability to create from scratch. Also available for the iPad. Integrated and prints directly to Shapeways.
Learn how 123D Design and Shapeways work together
Windows, Mac, Online Service

Tinkercad
A fantastic beginner program, that leads you to learn complex things through simple quests. Runs right in your browser, and the skills you learn are easily transferable to more advanced programs. Integrated and prints directly to Shapeways!
Learn how Tinkercad and Shapeways work together
Online Service

Windows, Mac, Online Service

Tinkercad
A fantastic beginner program, that leads you to learn complex things through simple quests. Runs right in your browser, and the skills you learn are easily transferable to more advanced programs. Integrated and prints directly to Shapeways!
Learn how Tinkercad and Shapeways work together
Online Service

3D Tin
Another browser based program using WebGL, this is free as long as you share your designs under Creative Commons.
Online Service

FreeCAD
An open source parametric 3D modeler, great for both the home user, hobbyist and experienced designer. Parametric modeling allows for easy editing of your design.
Windows, Mac, Linux

Sculptris
A free, introductory digital sculpting tool, a great stepping stone for digital sculptors, created by the makers of Zbrush.
Windows, Mac

Sketchup
Drawing-based tool for architects, designers, builders, makers and engineers who design for the physical world. SketchUp Make is a free version and SketchUp Pro is a paid version with additional functionality.
Windows, Mac

3D Model To Print
A cloud-based software service, focused on 3D architectural models. 3DMTP automatically and efficiently transforms 3D designs into scalable and 3D printable model files.
Online Service

A cloud-based software service, focused on 3D architectural models. 3DMTP automatically and efficiently transforms 3D designs into scalable and 3D printable model files.
Online Service

eMachineShop
Easy-to-use for designing mechanical parts - a machine shop at your fingertips! With its intuitive interface & helpful videos, anyone can leverage both the Shapeways and eMachineShop production facilities by using just one tool.
Windows, Mac, Online Service
Source from : https://www.shapeways.com/creator/tools