Widelands 17

Widelands is an open source (GPLed) real-time strategy game. It is built upon the SDL and other open source libraries and is under heavy development.
Main features:
- Four Worlds (Tile Sets) (Greenland, Winterland, Blackland and Desert)
- Three Tribes (Barbarians, Imperials and Atlanteans)
- Several playable single player (tutorial) missions
- Maps for single and multiplayer mode
- Save and load of single and multiplayer games
- Ability to build a settlement from scratch
- Military and warfare (Attacking, Training, defending, conquering of military buildings)
- A map editor, to build your own maps and campaigns