Roleplay and how to do it.
Perhaps not a drawing guide, but here’s a website that has almost absolutely everything you need to know about roleplay, and within are several links to drawing anatomy… and more personal anatomy if you look in the second link.
Anatomy for boys and girls (warning on this one, no direct images but nonetheless wouldn’t recommend this for work):
This site is extremely good for new roleplayers and older ones looking to spice things up. I personally recommend it :)