past simple

gammar
http://www.curso-ingles.com/gramatica-inglesa/pasado.php

www.curso-ingles.com/gramatica-inglesa/pasado.php

exercises
http://www.myenglishpages.com/site_php_files/grammar-exercise-simple-past.php#.Uzp3LaKLUuA
http://www.ego4u.com/en/cram-up/grammar/simple-past

present and past perfect

http://www.englishpage.com/verbpage/verbs12.htm
http://www.englishpage.com/verbpage/presentperfect.html
http://www.tolearnenglish.com/exercises/exercise-english-2/exercise-english-10277.php
http://www.curso-ingles.com/ejercicios-test-ingles/present-perfect-past-simple.php

present and past continious

http://www.englishexercises.org/makeagame/viewgame.asp?id=2935
http://www.englishpage.com/verbpage/pastcontinuous.html
http://www.leshoekje.be/leshoekje/ICT-oef%20ENG2/present-past3.htm
http://www.englisch-hilfen.de/en/grammar/past_progressive_verbs.htm

should, must, have to

grammar
http://www.aulafacil.com/Ingejerc/Lecciones/Lecc26.htm
exercises
http://www.aulafacil.com/Ingejerc/Lecciones/Ejerc26.htm

http://www.englishexercises.org/makeagame/viewgame.asp?id=6270

http://www.englishexercises.org/makeagame/viewgame.asp?id=3401