More practice: present perfect vs simple past

http://www.esl-lounge.com/student/grammar/2g11-past-simple-present-perfect-gap-fill.php

http://www.agendaweb.org/verbs/present-perfect-simple-past-simple-exercises.html

http://www.perfect-english-grammar.com/support-files/present_perfect_or_past_simple_2.pdf

http://www.grammarbank.com/present-perfect-exercises.html