This in a book: [link]
Full tutorial list: [link]

Please read the following description, as it's part of the tutorial. First I want you to realize that the ideal body proportions used to learn anatomy are essential to the learning process (it simplifies a very complex subject for the student), but that you are not expected to abide by them at all times. I for one draw bigger heads and longer necks. It's just not noticeable (not always at least) because I'm familiar enough with anatomy to bend the rules without breaking them. Once you have integrated these rules, you too will veer from them to develop your own style – but I honestly don't recommend skipping ahead.

I am also aware of the fact the different human groups around the world have very different body features, and that is another tutorial I'm working on, one I'm quite excited about! So stay tuned for that.

Second, I'm going to repeat here what I said in the original tutorial: Use the above guide as a supplement to gesture drawing. Reading and memorizing all this won't help you as much as sketching from life; this guide simply provides the understanding that will make your sketchign a learning experience ratehr than a random process. So, carry a sketchbook around and gesture-draw people around you, especially people in motion. This way you are forced to use fast gesture drawing and not go obsessive over the details, and that is how you can achieve a solid grounding in grasping form and movement before moving on to worrying about surface additions such as clothing and expression. Think of the human body as an assortment of volumes, not as lines put together. This will change your life, trust me.

Now about the tutorial itself. It is large, so if you find it intimidating do start with my much smaller guide right here: [link]
Also, I realize the format may be hard to deal with on screen. Please bear with me, as I did my best to conciliate screen use and a print of this, for those who would like to have this as a reference poster to hang by their work table (this will be available shortly and I'll make it as cheap as I can, promise).

Special thanks to ~stukchocolat for his help with face proportions.

Bibliography:
Drawing the Head and Figure, Jack Hamm
Le dessin anatomique facile, Burne Hogarth
Experience and (believe it or not) martial arts education