http://www.englisch-hilfen.de/en/exercises/active_passive/passive_sentences1.htm
http://www.englisch-hilfen.de/en/exercises/active_passive/sentences_simple_past.htm
http://www.englisch-hilfen.de/en/exercises/active_passive/sentences_simple_present.htm
http://www.ego4u.com/en/cram-up/grammar/passive/exercises
http://www.ego4u.com/en/cram-up/grammar/passive/exercises?02
http://www.ego4u.com/en/cram-up/grammar/passive/exercises?simple-present
http://www.ego4u.com/en/cram-up/grammar/passive/exercises?simple-past
http://www.ego4u.com/en/cram-up/grammar/passive/exercises?present-progressive
http://www.ego4u.com/en/cram-up/grammar/passive/exercises?past-progressive
http://www.ego4u.com/en/cram-up/grammar/passive/exercises?simple-present-2
http://www.ego4u.com/en/cram-up/grammar/passive/exercises?simple-past-2
http://www.ego4u.com/en/read-on/countries/usa/tour/washington#exercises