I had a very intense, disturbing experience in Second Life last night.
I went to see the Virtual Hallucination simulation that has been developed by UC Davis. It has been designed to give us a better understanding of what it feels like to have schizophrenia. Based on the stories of two people who have schizophrenia, it aims to provide an auditory and visual experience that simulates how schizophrenics see and hear the world.
To my mind this is the most powerful teaching/learning experiences in Second Life - it moved and disturbed me. If you have any interest in mental health, especially if you are a health professional working in the area I would recommend you visit this place. But be warned that it is an intense experience.
If you cannot access Second Life, have a look at this video which will give you a feel for the place.