Blender is a free, open-source tool for creating and animating 3D content. It is available for all major operating systems. It allows the creation and modification of graphics primitives, surfaces, etc. along with lighting and dynamic camera features. Animating is done via keyframes, and most properties can be animated over time. Advanced features include interactivity (e.g., game-like features), particle systems, skeleton-based models. Blender includes and is partially based upon a Python scripting system.
Free (and open-source).
Available for all major operating systems: Windows (32- and 64-bit); Linux (32- and 64-bit); Mac OSX (PowerPC and Intel); Solaris; and Irix.
Blender makes 3D content, which can be rendered as images or animations. In addition, it can export 3D data directly. 2D formats include: TGA, JPG, PNG, OpenEXR, DPX, Cineon, Radiance HDR, Iris, SGI Movie, IFF, AVI and Quicktime GIF, TIFF, PSD, MOV (Windows and Mac OS X). 3D formats include: 3D Studio, AC3D, COLLADA, FBX Export, DXF, Wavefront OBJ, DEC Object File Format, DirectX, Lightwave, MD2, Motion Capture, Nendo, OpenFlight, PLY, Pro Engineer, Radiosity, Raw Triangle, Softimage, STL, TrueSpace, VideoScape, VRML, VRML97, X3D Extensible 3D.
Integrating with other Tools
Blender is a powerful program! The learning curve is quite steep, but this is ameliorated by the wealth of good online tutorials, many in video format (e.g., on YouTube). There is a large and vibrant user community, which means that instruction is easy to find, on practically any topic of interest.
To take advantage of Blender, the user should have a 3-button mouse. It can be used otherwise (e.g., with a laptop one-button trackpad), but it is simpler with a 3-button mouse.