Art of Illusion
Java
Art of Illusion is a free, open source 3D modelling and rendering studio. (GPL)
Blender
Linux, UNIX, Windows, MAC OS X
Blender is the free open source 3D content creation suite, available for all major operating systems under the GNU General Public License. (GPL)
breve
Linux, Windows, MAC OS X
breve is a free, open-source software package which makes it easy to build 3D simulations of multi-agent systems and artificial life. (GPL)

BRL-CAD
Linux, UNIX, Windows, MAC OS X
BRL-CAD is a powerful cross-platform Open Source combinatorial Constructive Solid Geometry (CSG) solid modeling system (BSD)
gSculpt
Windows, Linux
gSculpt is an open source procedural 3D modelling application with a comprehensive set of polygon mesh editing tools. (GPL)
K-3D
Linux, UNIX, Windows
K-3D is a free Open Source 3D modeling and animation software. (GPL)
KPovModeler
Linux, UNIX
KPovModeler is a modeling and composition program for creating POV-Ray scenes in KDE. (GPL)
MeshLab
Linux, UNIX, Windows, MAC OS X
MeshLab is an open source, portable, and extensible system for the processing and editing of unstructured 3D triangular meshes. (GPL)
Misfit Model 3D
Linux, UNIX, Windows, MAC OS X
Misfit Model 3D is an OpenGL-based 3D model editor that works with triangle-based models. (GPL)
Pixie
Linux, UNIX, Windows, MAC OS X
Pixie is an open source RenderMan renderer for generating photorealistic images. (LGPL)
QCAD CE
Linux, UNIX
QCAD is an application for computer aided drafting in two dimensions (2d). With QCAD you can create technical drawings such as plans for buildings, interiors, mechanical parts or schemas and diagrams. (GPL)
White_dune
Linux, UNIX, Windows
White_dune is program to change or create VRML97/VRML2 files. (GPL)
Wings 3D
Cross-platform
Wings 3D is a subdivision modeler inspired by Nendo and Mirai from Izware. (BSD)
Popularity: 10% [?]