Blender - Blender is the open source, cross platform suite of tools for 3D creation.
Pmx Editor - PMX Editor is for editing 3D model data to be used in MikuMiku Dance.
Sculptris - Sculptris: Enter a world of digital art without barriers.
3DTin - 3DTin is a browser based 3D modelling tool.
Misfit Model 3D - Misfit Model 3D is a 3D model editor that basically operates with triangle-based models.
DeleD CE - DeleD is a 3D modeler and level-editor combined into one.