http://www.englishexercises.org/makeagame/viewgame.asp?id=3053
http://www.agendaweb.org/verbs/tobe/
http://www.eflnet.com/grammar/tobepresent.php
http://www.adelescorner.org/grammar/present_simple/to_be.html
http://www.myenglishpages.com/site_php_files/grammar-exercise-be-present.php
http://perso.ya.com/mjandres/archivos/presntbe1.htm
http://www.kico4u.de/english/uebungen/5klasse/findbe.htm
http://activiscope.com/flash_new.php?activity=aztec&id=21699
http://www.englishexercises.org/makeagame/viewgame.asp?id=1018
http://www.englishlearninggames.com/to-be-am-is-are-game-for-the-beginners.html