passive voice all tenses

http://www.esl-classroom.com/grammar/passive2.html

active to passive

http://eslus.com/LESSONS/GRAMMAR/PASSIVE/Gramc.htm

passive voice

http://esl.fis.edu/grammar/single/passive_r.htm

active to passive

http://www.english-4u.de/passive_ex1.htm

active to passive

http://www.ego4u.com/en/cram-up/grammar/passive/exercises?simple-present

passive to active and active to passive

http://www.esl-classroom.com/grammar/passive6.html

active to passive

http://wwwedu.ge.ch/cptic/prospective/projets/anglais/exercises/passive1.htm

active to passive

http://www.redcamelot.com/camelot/exercises/SEPT26/Grammar/Passive%20Voice/Exercise%201.htm

active to passive

http://www.esl-classroom.com/grammar/passive1.html

passive voice

http://www.esl-classroom.com/grammar/passive5.html

passive voice

http://www.ego4u.de/de/cram-up/grammar/passive/exercises?simple-past

passive voice

http://eslus.com/LESSONS/GRAMMAR/PASSIVE/Gramb.htm

passive voice

http://www.english-grammar-lessons.com/passive/exercise2.swf

Third conditional

http://www.perfect-english-grammar.com/third-conditional-exercise-1.html

present simple

http://www.ego4u.com/en/cram-up/grammar/simple-present/form/exercises

present simple

http://www.englishmaven.org/HP6/Present%20Tense%20Exercise%205.htm

present simple

http://personales.ya.com/mjandres/archivos/ps1.htm