chessblogger: Chess Position Trainer 4 – Public Beta is out

Chess Opening Basics: The Scotch Game - Chessable Blog

Chess Position Trainer - Study and Practice Chess Openings

The Slav Defense for the Tournament Player: Expert Knowledge - Chess Opening Software on DVD

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 Openings Trainer Lite for Android - Download

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

Foxy Openings - Volume 180 - Domination Studies - Bernhard Horwitz for the Tournament Player - Vol. 3

CHESS BOOK: CHESS OPENING TRAP OF THE DAY by Bruce Alberston 9781580422178

Chess Opening Trainer App Price Intelligence by Qonversion