Move Trainer App? : r/chess

Daniel Fernandez: Weapons against the Caro Kann - Vol. 1 & Vol. 2

Web Apps

Chess Openings Pro - Apps on Google Play

Training Tactics with Chess Position Trainer - Best Combinations of 2014

Chess Position Trainer Tutorial: Using Chess Engines

GitHub - davidgma/chess-opening-trainer: Obsolete: Training program to help learn chess openings.

Lichess just added opening training (in addition to their tactics trainer). Check it out! : r/chess

Opening training with Fritz 17

Catastrophes & Tactics in the Chess Opening Workbook - Vol 1: Indian Defenses: Tactical puzzles to help exploit opportunities and avoid disasters in (Winning Quickly at Chess Workbook Series): Hansen, Carsten

I made an interactive trainer for learning the queens gambit opening, including 86 variations : r/chess