http://www.cybernetworlds.com/ looks like a virus with just a link to download, but it's actually a version of activeworlds that's dead, much like worlds.com (posted in here before i believe).
it's pretty big and there's usually 0 people online, maybe 1 in a world that you need to buy membership for (which i don't think is possible anymore). this guy i knew explored it 2 years ago when there were still a couple people around and apparently they had some virtual church going where they would gather in a church somewhere in the world and use microphones to have a preaching session or w/e churches do.
quote from another person who played "it's a damn ghost town with random sounds of people getting a strike in bowling"
more dead activeworlds clones:
http://www.outerworlds.com/http://www.3dee.com/