Here you have some links with online exercises for practising:
PASSIVE (PRESENT SIMPLE)
PASSIVE (PAST SIMPLE)
- http://www.ego4u.com/en/cram-up/grammar/passive/exercises?02
- http://www.englisch-hilfen.de/en/exercises/active_passive/sentences_simple_past.htm
- http://www.perfect-english-grammar.com/passive-exercise-2.HTML
- http://www.englishexercises.org/makeagame/viewgame.asp?id=4947
PASSIVE (PRESENT CONTINUOUS)
- http://www.englishexercises.org/makeagame/viewgame.asp?id=4945
- http://www.ego4u.com/en/cram-up/grammar/passive/exercises?present-progressive
- http://first-english.org/english_learning/english_active_passive/82_passive_present_continuous_exercises.htm
And here you have a game:
http://www.eslgamesplus.com/passive-voice-past-passive-esl-grammar-sentence-activity-fun-game-online/