For tactics I've never seen anything better than chess tempo [0], which is free, or for a small yearly subscription you can absolutely go nuts breaking down tactical themes and combinations of themes, and the tracking is very good. I did several thousand tactics puzzles there and it helped quite a bit.

For books, Beginners Mind by Jeremy Silman is pretty good, as is his endgame book. Logical Chess by Cherenev is also a great introduction to how skilled people think about games but takes a different approach than Silman.

[0] - http://chesstempo.com/

Tactics: https://en.lichess.org/training Video library: https://en.lichess.org/video

I found http://www.chesscademy.com pretty helpful. It takes a MOOC approach to chess, while keeping things fun and manageable.

I learned a lot from the tutorials by Joshua Waitzkin in Chessmaster: Grandmaster Edition. I heard that lichess has some puzzles as-well, but never tried them.

for books starting from scratch or nearly from scratch, I have enjoyed the "winning chess" series by Yasser Seirawan