These sites i researched today are the ones i think are amazing for different ages of children.

Children 6-11
1. Club Penguin
2. Build-a-bearville
3. Kidsites

Pre-Teens 12-14
1. (Possibly if allowed, Myspace)
2. (Club Penguin, Possibly)
3. Zwinky

Teens 15-21
1. Myspace
2. Meez
3. IMVU (This is a download, not a website)