→ Open source, Ad-free chess server. It features tactics, opening and coordinate trainers. Blitz, atomic, 3-check, horde, chess 960, King of the Hill; standard or antichess, live or correspondence. 100% free, no premium accounts to speak of. It's the best site for playing chess at a club level, the only downside is a smaller player pool. It runs stockfish 8.
→ Lectures by titled playershttps://www.youtube.com/user/thechesswebsite
→ Openings, key concepts behind them, some middle game theoryhttps://www.youtube.com/user/KebuChess
→ Openings (with a lisp)https://www.youtube.com/user/kingscrusher
→ Analysis of master games https://www.youtube.com/user/ChessNetworkhttps://www.youtube.com/user/chessbrah
→ Eric Hansen's channel, not very instructive but somewhat entertaining
Required reading (I am not sure I can post links):
-Matanović's Encyclopedia of chess openings
-My system by Aron Nimzowitsch
-Kasparov's Chess Puzzle Book
-Dvoretsky’s Analytical Manual Post too long. Click here to view the full text.