VCS is a visual d20 3.5 combat program for dungeon masters. If you have dual monitors, one can show the DM map and the other the player's. It is possible to 'hide' things, and the players will only see what's in range or what they've seen before. After drawing the map, players can be moved, and over 850 standard monsters selected from for them to fight. Huge maps can be drawn and filled with monsters very quickly.
MV3D is a virtual world and multi-player game framework for use with Python. It was designed with scalability in mind and is able to distribute a world across as many servers as needed while dynamically balancing the load. The simulation framework is not specifically slanted towards any one genre of online game or virtual world, and can just as easily be used for a space game as a fantasy setting. Objects on an MV3D server can be simulated using the ODE physics engine for realistic interactions. A single server is able to host thousands of of simulated objects. The client works with both the Ogre3D and Panda3D renderers.
AYUMiS is a project aiming to create a cross-platform MMORPG set in space. It is developed in C++ with ClanLib. It will give the player full control over the game universe, with no NPCs or pre-planned storyline. It attempts to give the player a full range of choices and open-ended gameplay.