Titania is a X3D/VRML editor and browser. It's intended to become a fully standard-compliants X3D renderer for future Ubuntu releases. It already completely implements the Moving Worlds specification for VRML 2.0, and most parts of the X3D spec. Titania can also be used as 3D viewer for .wrl files, as 3D rendering engine, data visualization, and even as game engine. It comes with x3dtidy for beatifying X3D/VRML files.
AGK is a easy to learn and embed C++ toolkit for writing games. It utilizes Boost, provides many API classes and functions, 3D sound features, integration with screen readers (like JAWS) or eSpeak synthesizer or MS Speech API, NVDA, Window Eyes, system access, INI-style configuration, console I/O, an ready to use game menu, OpenGL and built-in window management, hashing functions, number conversion, and a custom memory manager, and an interpreter for AngelScript.
delta3d is a game and simulation engine. It integrates Open Scene Graph, Open Dynamics Engine, Character Animation Library, OpenAL, and Qt in an easy to use API.