Games/Online Activities that Teach History

PBS Scavenger Hunt Through History:
http://www.pbs.org/wnet/historyofus/tools/scavenger/game2_flash.html
China Game:
http://asiasociety.org/node/8688
Historical Tweets:
http://historicaltweets.com/
History Games:
http://playinghistory.org/items/index/page/1