Try www.starfall.com it's fun and educational, you can also try http://barbie.everythinggirl.com/ Have fun and enjoy!
If this is for a child I would suggest goop. It's easy to make and the kids can enjoy right away or you can give as party favors. I would suggest buying the neon food coloring to match for your party.
scholastic is one of the best websites
I think facebook,twitter,and myspace are good websites but mostly for teens.Out of those I would suggest facebook for kids.Because alot of people go on it at my school and..i'm a kid.Lol.A really safe website I mostly suggest for kids and also teens is www.kidzworld.com .It's really fun its like a kid [and teen] facebook.You make friends,comment them,decorate ur profile,and more!Also for younger girls I suggest girlsgogames.com.And for kids and/or teens I suggest clubpenguin.com or habbo.com.
A good website for girls (kids) is gamesforgirls.com
KidzSearch.com is a good resource for kids websites.
bered.com
imvu.com is a good one
scary for kids
Fantage is a good one.
Clubpenguin
A list of cool online websites for older kids are...Miniclip.comAddictinggames.comSteamcommunity.comRunescape.comThat's all I can think of right now, I suggest buying your son or whatever a PlayStation 3 or Xbox 360.
there is a website called Brainnook where kids get to have friend and chat with them under a guideline also they get to play math and language games.