http://www.synonym.com/antonyms/  (synonym/antonym finder)

 

http://www.youtube.com/watch?v=F5XJuH57tf0 (antonym song)

 

http://www.arcademics.com/games/frog/frog.html (game)

 

http://www.learninggamesforkids.com/vocabulary-games/antonyms/intermediate-adjective-antonyms.html (game)

 

http://gamequarium.org/readquarium/antonyms.html  (variety of games)