Blender - Blender is the open source, cross platform suite of tools for 3D creation.
Bforartists - Bforartists is a fork of Blender.
MakeHuman - MakeHuman is a free, open source, interactive modeling tool for creating custom 3D human characters.
Art of Illusion - Art of Illusion is a free, open source 3D modelling and rendering studio.
Topogun - TopoGun is a stand-alone resurfacing, and maps baking application.
MagicaCSG - MagicaVoxel Official Website