Blender - Blender is the open source, cross platform suite of tools for 3D creation.
Resolume - Resolume is an application for live video performances.
FreeCAD - An open-source parametric 3D modeler
Mapping Matter - Web Based creative tool for technical designers
Sculptris - Sculptris: Enter a world of digital art without barriers.
Isadora by TroikaTronix - Isadora is the award winning, interactive media presentation tool that allows you to do just about anything you like.