This is a very personal list of installations in virtual worlds. Some are my own, and in describing them I try to demonstrate what I have learned in designing educational spaces; some are by others, and I often discuss why I found them instructive, interesting, or just really cool. Installations come and go, so older links might not work, but there are a surprising number of sites that have been continuously available over the past decade or so.
There is a movement among Second Life educators to archive their works. As I find out about this, I will post things here.