Chess Position Trainer - Study and Practice Chess Openings

ChessBase Software Fritz Trainer Chess Opening Vienna With 3.f4 by Nigel Davies for sale online

Chess opening training - Chess Tempo opening trainer

Chess Position Trainer Tutorial: Using Chess Engines

OMGChess: More on Learning Openings

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

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

Chess Prep - openings trainer by Tomasz Bogun

chessblogger: Chess Position Trainer 4 – Public Beta is out

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

Edit Opening Chess Openings Trainer