http://www.englisch-hilfen.de/en/exercises/tenses/simple_past_mix.htm
http://www.eslgamesplus.com/verb-tenses-interactive-grammar-game-for-esl-jeopardy-quiz-game/
http://www.perfect-english-grammar.com/irregular-verbs-exercise-1.html
http://www.myenglishpages.com/site_php_files/grammar-exercise-simple-past.php
http://www.eslgamesplus.com/action-verbs-present-tenses-esl-interactive-grammar-vocabulary-game/
http://www.verbs-online.com/english-verbs/english-verbs.htm
http://www.curso-ingles.com/practicar/ejercicios/past-simple