Roll20 - Roll20 is a suite of easy-to-use digital tools that expand pen-and-paper gameplay.
Lichess - The complete chess experience, play and compete in tournaments with friends others around the world.
GOG.com - DRM-free game store, selling both new and old titles. No clients required.
Chess.com - Play chess on Chess.
Diep.io - Diep.io is a multiplayer action game available for web browsers, Android, and iOS, created by Brazilian developer Matheus Valadares. Players control tanks and earn points by destroying shapes and killing other players in a 2D arena.
Chessmaster - Chessmaster is a chess playing computer game series which is now owned and developed by Ubisoft.