This is a series of articles, originally written by Xoppa. You can find the original versions here:

• Basic 3D using libGDX
• Loading models using libGDX
• Loading a scene with libGDX
• Behind the 3D scenes - part1
• Behind the 3D scenes - part2
• Creating a shader with libGDX
• Using materials with libGDX
• 3D frustum culling with libGDX
• Interacting with 3D objects
• Using collision shapes
• 3D collision detection
• 3D physics simulation

These articles give you a good quick overview on how to achieve basic tasks with the new 3D API. For more information, take a look at the Javadocs of the classes in the com.badlogic.gdx.graphics.g3d package or check out the tests and demos.