Kodu Game Lab - Kodu lets kids create games on the PC and XBox via a simple visual programming language.
Castle Game Engine - An open-source 3D/2D game engine for ObjectPascal.
Wick Editor - The Internet's free and open-source creation toolkit.
Open 3D Engine - Open 3D Engine is an open-source 3D game development engine in real-time.
Scroller Game Creator - Create your scroller shooter game
WaveEngine - The definitive free cross-platform mobile engine to unleash your games using C#.