DOP

http://www.studyspanish.com/lessons/dopro1.htm (explicacion)

http://www.myspanishgames.com/fun-Spanish-grammar/direct-object-pronouns.html (explicacion)

http://www.softschools.com/quizzes/grammar/indirect_objects/quiz548.html

http://www.colby.edu/~bknelson/SLC/DO2.php  (good one)

http://www.quia.com/rr/62652.html

http://www.superteachertools.com/jeopardy/usergames/Feb201106/game1297467474.php (jeopardy)

http://www.quia.com/jg/453190.html

http://www.123teachme.com/learn_spanish/direct_object_pronouns

http://www.trentu.ca/academic/modernlanguages/spanish/masarriba/directobject.html