I haven't seen much nonprofit presence in other
virtual worlds, primarily because SL is the most developed and popular platform - even despite some of the technical glitches.
It has the most critical mass of educational, library, and nonprofit users.
I'm on a panel for the Horizon's Project - it is educational technology - and they are experimenting with emerging technology and educational projects. It is pretty amazing.
One of the areas they are exploring are virtual worlds
here
on the project wiki, you find a bunch of examples of virtual worlds projects in education. As you will notice, SL is the dominate platform.
For additional resources from the original horizon report about virtual worlds in education, see this
list of urls
Beth Kanter
Beth's Blog
[URL=http://beth.typepad.com[/URL]