Present Perfect - Simple Past : a few links

Explanations in French!

Present Perfect - cours : http://www.anglaisfacile.com/exercices/exercice-anglais-1/exercice-anglais-18.php

e-anglais.com : http://www.e-anglais.com/cours/present_perfect.html

Le Present Perfect Anglais : http://www.anglaiscours.fr/present-perfect-anglais.html

Explanations in English - recommended

Englishpage : http://www.englishpage.com/verbpage/presentperfect.html

Here is a brief review of the form and function of the present perfect tense. http://web2.uvcs.uvic.ca/elc/studyzone/410/grammar/pperf.htm

Explanation and tests : http://www.ego4u.com/en/cram-up/grammar/present-perfect-simple

etc. If you would like to do more exercises, just google present perfect and/or simple past.