TripleA - TripleA is a free (under GPL) turn based strategy game based on Axis & Allies board game.
eDominations - multiplayer strategy game
Warlight - Warzone is a customizable Risk-like strategy game where you compete with your friends to conquer the world.
eRepublik - eRepublik is a Free to play, Browser-based and Massively Multiplayer Online video game created and published by eRepublik Labs.
Domination - Domination is a game that is a bit like the well known board game of Risk.
NationStates - NationStates is an innovative, browser-based game that tries to simulate the real challenges and turmoils that come from trying to govern a modern state.