Yes second life
WebkinzMeezThere.com
meez
runescape
Xivio.com is great! Its a 3D no download free virtual world!!!
no
FreeRealms is a site where you must download it but it is totally free.
There are 2 that i know of dragonopia and evodragon
Poptropica
There is no world like Onverse. All virtual worlds out there are unique in their kind. About downloading, you shouldn't worry. Make sure the world you want to play is safe. Onverse.com is completely safe.
Animal jam.com and moshi monster.com also clubpenguin.
you walk around in your own virtual world
Animal Jam, another free world, unless you get a special membership.