present perfect & past simple

http://www.ego4u.com/en/cram-up/grammar/simpas-preper

http://www.aulafacil.com/Ingejerc/Lecciones/Lecc20.htm

http://www.englishpage.com/verbpage/verbs5.htm

http://www.curso-ingles.com/ejercicios-test-ingles/present-perfect-past-simple.php