I used Second Life as a way to talk to my students about virtual environments and technology. Using my own account, I would visit some of the sites on this list to show students examples of different types of virtual environments.
Please be aware that Second Life is an adult website. You may see advertising that is not appropriate for students as you "explore". The sites I have listed have minimal advertising and tend to be student-friendly.
You can extend the actitvity using the scavenger hunt. Again, I would do this with a small group of students, letting them take turns controlling the avatar in order to find the items on the list. I monitored this group closley to make sure they stayed on-task.
This is a great technology lesson to introduce at the beginning of the year so that you can talk about internet safety and advanced technology. It also became a favorite "prize" for students to earn Second Life time with me and a friend later in the year.