Jeff LaMarche has two great articles on proportions that are must reads if you are sculpting or drawing the human figure.
Canons of Proportion and the Ideal, Part 1 covers the systems of ideal proportions laid out through history. The Egyptians, Greek, Vitruvius, etc.
Canons of Proportions II - Faith-Based Canons? takes data from real people (in this case military personel) to determine what the real average human proportions and standard range most people fall into.