open3mod - A free, Open-Source 3D Viewer designed to make it all easier. Massive 3D Format support
Blender - Blender is the open source, cross platform suite of tools for 3D creation.
CtrlView - Fast, compact, powerful viewer/converter for different 2D/3D raster/vector file formats
Autodesk 3DS Max - 3ds Max is software for 3D modeling, animation, rendering, and visualization. Create stunning game enrivonments, design visualizations, and virtual reality experiences.
Cinema 4D - Cinema 4D is a 3D modeling, animation, motion graphics and rendering application.
MilkShape 3D - The MilkShape 3D website has been down for almost one week.