Using a 3D modeling program 7 to tessellate a smoothed 3D polygon box and extrude its facets is a lot like molding a piece of clay. Human figures (as well as animals) can be modeled rather quickly and easily using this simple technique. Here are some inexpensive books that can help with figure modeling:
Drawing the Head & Figure by Jack Hamm
This book has hundreds of illustrations to help with your human figure design. It even covers clothing for men and women.
How to Draw Animals by Jack Hamm
Deals with the shapes and muscle forms of various animals.
How to Draw Comics the Marvel Way by Stan Lee and John Buscema
Great for modeling heroic figures and giving them dynamic poses for more dramatic scenes.
STOP STARING: Facial Modeling and Animation Done Right by Jason Osipa
I you plan to animate your model's face, this book will show you how best to model your 3D head from scratch to get the best possible pulling and stretching for perfect expressions.
Building A Digital Human by Ken Brilliant
This book literally describes the step-by-step method of modeling a 3D human figure. It covers the smallest details in how to organize your polygons for making realistic hands and feet. And the book advances as your skill advances.
An Atlas of Anatomy for Artists by Fritz Schider
This book contains illustrations from masters such as Leonardo, Rubens, Michelangelo, Vesalius, and others. A great reference for detailed muscle work and skeleton posing.