for children

British Council - very nice activities
http://www.britishcouncil.org/kids.htm

Frog - past verbs
http://www.english-online.org.uk/games/pasttense.htm

quick click bricks
http://www.english-online.org.uk/games/gamevocab.htm

the description detective
http://www.english-online.org.uk/games/findPerson.htm

vocabulary jungle
http://www.english-online.org.uk/games/vocabblock.htm

English star
http://www.english-online.org.uk/games/vocabexpertp1.htm

noun, verb or both?
http://www.english-online.org.uk/games/verbnounboth.htm

for real kids
http://www.eslkidstuff.com/OnlineGamesMain.htm

English for Fliers
http://www.marks-english-school.com/games.html

Crosswords for Kids
http://notredamke.rkc.si/english/crosswords/Crosswords.htm