facebook is one
Redtube is a very popular site among 11-year olds.
Roblox
There many websites for teenagers dating. Probably the most famous one is Tagged.
funbrain.com
yes
Usually it's either baseball or basketball.
Well, it honestly depends on the ten year old. But some clean websites that are fun for younger kids include disneychannel.com, nickelodean.com, and millsberry.com.
There are plenty of websites suitable for 13 year olds. Facebook and Twitter both allow 13 year olds to use their sites, but it really depends on the child and how mature he/she is.
You can be on Everloop as soon as you turn 8. It's for 8 to 13 year olds.
Hotmail
Myyearbook.com
boohoo.com