MakeHuman is an interesting multiplatform program, completely free, that offers you the chance to create 3D models in an innovative way and with professional quality. The things that make this program unique are the new GUI tetra-parametric components and the Natural Pose System for advanced muscle simulation. With this you get models that seem real. Making a model that looks photorealistc only takes a few minutes.
MakeHuman has intelligent resources. For example: if you are modelling a woman, if you increase her weight, it affects the whole of her body.
MakeHuman also lets you simulate muscular movements very precisely, thanks to a series of algorithms.
A program that is worth downloading (this version here is for Windows).