Open source simulation game based on Transport Tycoon Deluxe
FlightGear Flight Simulator: free open-source multiplatform flight sim
WW2 U-boat simulation
X3D is the open-standard format for 3D graphics scenes on the Web.
Online War system for IL-2 Sturmovik and Iron Front in ArmA 2
DIS(IEEE 1278.1) Fully Implemented in C++
C.S.R
C++ OpenGL 3D Game Dev Lib [moved to: play.ru.net/src]
a software project that tries to visualize people's social behaviour
3D Multiplayer Hover Soccer
Old style soccer game with many exciting features