Vue Pioneer is a great way to learn 3D.
Create still images, motion graphics and video special effects procedurally.
STL/GCode viewer and editor.
Convert Direct3D X files into 3DMF files.
123D Make lets you turn 3D models into real world creations made out of any flat material that you can cut.
Customize everything from layout to animatics.
Create and edit a polygonal 3D model.