I see blog posts from redblobgames posted sometimes and I really like how in-depth the explanations are. I remember reading about 2d height maps and map generation for a side project I was working on a while back and the explanations he gave for why he was using a particular algorithm were fantastic (in addition to the interactive demos):

http://www.redblobgames.com/maps/terrain-from-noise/

http://www-cs-students.stanford.edu/~amitp/game-programming/...