Object pronouns

http://www.englishexercises.org/makeagame/viewgame.asp?id=1965
http://a4esl.org/q/h/9901/jd-pronouns.html

http://www.ego4u.com/en/cram-up/grammar/pronouns/exercises?02=

http://www.englisch-hilfen.de/en/exercises/pronouns/personal_pronouns3.htm