Blender is a free open source 3D creation suite. It supports 3D modeling, rigging, animation, simulation, rendering and compositing, just to list its key functions.
Blender is made by hundreds of people from around the world – both studios and individual artists, professionals and hobbyists, game artists and many others. They publish a lot of useful tutorials to help you get started. Have a look at this one as a taster:
Here you can download Blender for free.