SketchUp - 3D for Everyone
Blender - Blender is the open source, cross platform suite of tools for 3D creation.
SolidWorks - Dassault Systèmes SolidWorks Corp. develops and markets 3D CAD design software, analysis software, and product data management software. SolidWorks is the leading supplier of 3D CAD product design engineering software.
FreeCAD - An open-source parametric 3D modeler
Sweet Home 3D - Sweet Home 3D is a free interior design application that helps to draw the plan of house, arrange furniture on it and visit the results in 3D.
Assetforge - Asset Forge allows anyone to create 3D models and 2D sprites using building blocks.