Chess.com

Needs some material here :—-

Lichess.org

Lichess is a free and open-source Internet chess server run by a non-profit organization of the same name. Users of the site can play online chess anonymously and optionally register an account to play rated games. Lichess is ad-free and all the features such as game analysis are available for free, as the site is funded by donations from patrons. Features include chess puzzles, computer analysis, tournaments and chess variants.

Listudy is a free open-source site which reads data from Lichess to generate an opening study trainer using repetition techniques (similar to the Fritz opening trainer).

YouTube 

There is a huge amount of video training material available.

Dan Heisman

One of the best online chess Tutors is Dan Heisman with numerous award winning books to his name including Looking for Trouble and World’s most instructive amateur game book. Dan has over 300 videos on his Youtube site :-

Nimzowitsch

There is great set of some 30 – 30 minute videos running through most of the material in that world renowned book MY System by Aron Nimzowitsch. 

Add more stuff ….