Passive

1. http://perso.orange.fr/raud.dugal/advenced/passive%20voice/passivevoice.htm
2. http://www.englisch-hilfen.de/en/exercises/passive_sentences1.htm
3. http://www.englisch-hilfen.de/en/exercises/passiv1.htm
4. http://www.englisch-hilfen.de/en/exercises/passiv3.htm

MODALS

1. http://a4esl.org/q/h/0101/ig-modals.html
2. http://www.eslus.com/LESSONS/GRAMMAR/MODALS/Modala.htm
3. http://www.eslus.com/LESSONS/GRAMMAR/MODALS/Gramb.htm
4. http://www.eslcafe.com/quiz/modal1.html
5. http://grammar.ccc.commnet.edu/grammar/cgi-shl/quiz.pl/modal_quiz.htm