Exercises in Passive

http://www.tolearnenglish.com/exercises/exercise-english-2/exercise-english-50762.php

http://www.tolearnenglish.com/exercises/exercise-english-2/exercise-english-85627.php

Passive voice speaking activities:
http://www.onestopenglish.com/support/ask-the-experts/grammar-questions/grammar-passives-in-conversation/154058.article#ID_1

http://elt.oup.com/student/headway/int/a_grammar/unit07/hwy_int_unit07_2?cc=ca&selLanguage=en