Passive voice

Verb table:

http://www.englishpage.com/verbpage/activepassive.html

Excercise:

http://grammar.ccc.commnet.edu/grammar/quizzes/passive_quiz.htm

More exercises:

http://www.englisch-hilfen.de/en/exercises_list/passiv.htm

Video tutorial (10 min.)

https://www.youtube.com/watch?v=Qe6dHB0MC94