Lichess - The complete chess experience, play and compete in tournaments with friends others around the world.
TripleA - TripleA is a free (under GPL) turn based strategy game based on Axis & Allies board game.
Chess.com - Play chess on Chess.
Warlight - Warzone is a customizable Risk-like strategy game where you compete with your friends to conquer the world.
Fritz - Fritz is the world’s most popular chess program, developed by ChessBase, “the world's leading...
Domination - Domination is a game that is a bit like the well known board game of Risk.