OverThrown!

Freeciv is an open-source, turn-based strategy game based on Civilization II. Inspired by the history of human civilization, the game commences in prehistory and your mission is to lead your tribe from the stone age to the space age...

C-evo is a freeware empire building game for Windows

UniWar is a turn-based strategy game where players battle it out on the field with units of differents races, building bases and using the terrain to overcome their opponents towards victory. Several modes are available along with many maps to play.

webDiplomacy is a multiplayer, online version of Diplomacy, the popular turn based strategy game in which you battle to control Europe; to win you must be diplomatic and strategic.

Dominus is a free multiplayer browser strategy game. Grow in power by conquering other player's castles and making them your vassal. Vassals send their lord part of their income. Make everyone in the game your vassal to become the Dominus.