We have a from-scratch tutorial for OpenSG on this wiki, here are the individual pages:

OpenSG 2.0

1. Introduction
2. First Application
3. Basics
4. Node cores
5. Geometry
6. Light
7. Windows and Viewports?
8. Traversal?
9. Multithreading?
10. Clustering?
11. Modelling?
12. Find Memory leaks
13. Using the fcd2code generator
14. Creating a new container type
15. Debugging Tips
16. Tips for porting from 1.x

We also have the slides from the "Hands On with Open/Free VR Packages:OpenSG & VRJuggler" course given at IEEE Virtual Reality 2009 attached to this page .

For reference, here is the original tutorial for OpenSG 1.x:

OpenSG 1.x

1. Introduction
2. First Application
3. Basics
4. Node cores
5. Geometry
6. Light
7. Windows and Viewports
8. Traversal
9. Multithreading
10. Clustering
11. Modelling
12. Find Memory leaks