I like this site... but with all the ads(especially in the math arcade ads pop up when you lose a game) kids might be to tempted to click on stuff , sending possibly MALICIOUS viruses in the computer.
FunBrain is an awesome website that has fun games and also teaches good educational lessons on math and reading (hence the name). No sex, language, or violence (unless you consider hitting penguins with snow-balls violence).
Highly reccomended!