Weeworld and meez.
No, all virtual worlds require software to download.
One is girlsgogames.com. Those are just games. Virtual worlds? I am not sure if this is correct, I hear habbo.com? Best I could do sorry.
You can try Smallworlds.
The Earth
not that I know of.
Meez!
Try Xivio.com, its a free 3D virtual world! No download too!
There is only one, Xivio. It is free, no-download, and 3D.
Xivio.com is great! Its a 3D no download free virtual world!!!
Club BK mcWorld dragonfable adventurequest mechquest warpforce
It is poptropica.
Really, if you want to build virtual worlds, you'll have to download a game. Or you could go to a store and buy one. I would suggest Minecraft, it is pretty good and considered one of the best games of all time.