FlightGear Flight Simulator: free open-source multiplatform flight sim
Model Railway CAD program
HARFANG 3D source code public repository
Simple and intuitive 2D vector drawing for electronics and not only.
Character animation system for games and simulations.
A Realistic and Rich 3D Environment
X-Plane plugin which controls the Saitek Instrument Panel
(Moved to http://code.google.com/p/igb/)