OSGEdit is an editor of 3D scenes for games, scientific applications, and real-time simulations, using the OpenSceneGraph (OSG) library.
OSGEdit allows easy scenegraph editing for anyone using OpenScenegraph in some 3D project.
OpenSceneGraph is a free (LGPL) library that implements professional 3D scenegraph management, usefull for games, scientific applications, real-time simulations, etc.
Take in mind that It's only a scene editor/composer, not a modeller. You can use many programs (like Blender) to model your objects and import them into OSGEdit to compose a complex OSG scene for your application with switches lod's, etc.