Scott Eaton’s Bodies in Motion Reference Library
One of my all time favorite anatomy references is this handy dandy little webpage here. More than 750+ male and female photos in sequence? check. Outstanding b/w lighting on all of them? check. All SFW images but enough skin showing where the muscle placement is? check. Contortion, fencing, parkour and other poses included? checkity-check.
All of that for free? Aw yeah.
Go take a look around. ;D