Right now I'm trying to find out the average thigh diameter of a 20 year old man measuring from left to right. I'll need a lot of other measurements too, so I'm looking for a website with tons of average measurements for men and women of all ages. There's got to be such a thing right? It's the internet after all.

Anthropometric reference data for children and adults (2007 - 2010)

This document should provide you with the necessary search terms for chasing up further measures as well providing you a starting point. Good luck.