a game programming library for C/C++ developers distributed freely, supporting the following platforms: DOS, Unix (Linux, FreeBSD, Irix, Solaris, Darwin), Windows, QNX, BeOS and MacOS X. It provides many functions for graphics, sounds, player input, etc..
Hardware accelerated 2D full featured middleware for all who want to develop commercial quality 2D games rapidly and easily. It covers all imaginable 2D game genres (DirectX)
open source high performance realtime 3D engine written and usable in C++ and also available for .NET languages. It is completely cross-platform, using D3D, OpenGL and its own software renderer.