BrainKing is a popular online game system which supports more than 100 board games and variants (predominantly abstract strategy), which you can play against live opponents around the world. Basic membership is free and the site is fully localized to 20 languages.

http://BrainKing.com/

The Games

The games you can play on BrainKing (Total number of games and variants: 104):

• Chess family (33): Chess, Chinese Chess, Japanese Chess, Corner Chess, Fortress Chess, Horde Chess, Loop Chess (Chess with Shogi's piece capture and reuse concept), Anti Chess, Extinction Chess, Maharajah Chess, Three Checks Chess, Dark Chess, Atomic Chess, Janus Chess, Embassy Chess, Screen Chess, Crazy Screen Chess, Cylinder Chess, Amazon Chess, Berolina Chess, Fischer Random Chess, Legan Chess, Knight Relay Chess, Grand Chess, Capablanca Random Chess, Los Alamos Chess, Ambiguous Chess, Minishogi, Cheversi, Dice Chess, Recycle Chess, Ice Age Chess, Behemoth Chess
• Checkers family (10): Checkers, Anti Checkers, Czech Checkers, Corner Checkers, One Way Checkers, Parachute Checkers, Gothic Checkers, Turkish Checkers, Alquerque, Hawaiian Checkers
• Lines (19): Five in Line, Line4, Anti Line4, Linetris, Spider Line4, Pente, Keryo Pente, Small Pente, Small Keryo Pente, Open Pente, Open Keryo Pente, Spider Linetris, Pro Five in Line, Swap Five in Line, PahTum, Hasami Shogi, Connect6, Lines of Action, Scrambled Eggs
• Backgammon (8): Backgammon, Nackgammon, Anti Backgammon, Backgammon Race, Crowded Backgammon, Hyper Backgammon, Cloning Backgammon, Grasshopper
• Reversi (4): Reversi 6×6, Reversi 8×8, Reversi 10×10, Anti Reversi
• Ships (3): Battleboats, Battleboats Plus, Dark Battleboats
• Go (3): Go, Go 9×9, Go 13×13
• Espionage (5): Espionage, Small Espionage, Fast Espionage, Open Fast Espionage, Small Fast Espionage
• Other (19): Tablut, Tank Battle, Halma 8x8, Halma 10x10, Amazons, Jarmo, Froglet, Jungle, Anti Froglet, Sphere Froglet, Ludo, Breakthrough, Assimilation, Ataxx, Dice Poker, Triple Dice Poker, Frog Finder, Logik, Mancala