It is rare indeed that you come across a site which is professional, instructive, free and yet remains free of...

It is rare indeed that you come across a site which is professional, instructive, free and yet remains free of adverts. I guess wikipedia is one.
The one I came across yesterday for #python  lovers is http://thepythongamebook.com/en:pygame:start 

I have not found Pygame straightforward to learn but with this site it is a breeze! 
http://thepythongamebook.com/en:pygame:start