Blender

Blender is a software that is used for creating 3D content. Primarily this means you can make three dimensional images. However, you can also add sound, and make it time-based and interactive. This makes Blender ideal for a wide range of uses including creating 3D models, rendering, post -production, story boarding, creating animations, making movies, creating 3D 'programs', and making interactive environments and games.

It is a very powerful program and can be used by professionals and amateurs alike. 

Blender runs on many operating systems and is well supported on MacOSX, Linux, and Windows.