Blender is a free, Open Source modeling, animation and rendering tool. While earlier releases were infamous for having a steep learning curve, Blender 2.5 has turned the tables and now offers one of cleanest and most approachable user interfaces on the market.
Even though it’s as fully-featured as highly expensive commercial offering, Blender starts up in mere seconds and manages to stay snappy and responsive at all times.
Models can be created using traditional polygon modeling techniques, through sculpting or using procedural means. In addition to simple materials, Blender has a visual BRDF shader designer. Meshes can be UV unwrapped and materials can be painted on them. Animations support support shape and bone animation where Blender is equipped with several modular rigging systems such as BlenRig and Rigify.