Here is a list of online games and websites that will reinforce what they will be learning this year.
http://www.vocabulary.co.il/third-grade-vocabulary-games/
http://www.playkidsgames.com/games/pinball/pinball.htm
http://www.abcya.com/kids_technology_vocabulary.htm
http://www.abcya.com/dolch_sight_word_bingo.htm
http://www.gamequarium.com/evocabulary.html
http://www.ezschool.com/Games/CompoundWords.html
http://www.ezschool.com/Games/Adjectives.html
http://www.eduplace.com/kids/hme/k_5/quizzes/
http://www.gamequarium.com/sentencestucture.html
http://www.gamequarium.com/partsofspeech.html
http://teacher.scholastic.com/activities/bll/index.htm
http://www.bbc.co.uk/schools/magickey/adventures/patch_game.shtml
http://funschool.kaboose.com/fun-blaster/games/game_anagram_sleuth.html
http://funschool.kaboose.com/parent-teacher/3-4/games/index.html
http://funschool.kaboose.com/formula-fusion/animal-adventure/games/game_critter_jumble.html
http://www.storylineonline.net/
http://quizlet.com/204097/50-words-3rd-graders-should-know-flash-cards/