Practice
http://www.esl-lounge.com/student/grammar/2g11-past-simple-present-perfect-gap-fill.php
http://www.focus.olsztyn.pl/en-present-perfect-tense-exercises-with-answers.html#.WKN8FzvhDIU
http://www.really-learn-english.com/present-perfect-exercises.html
http://www.mes-games.com/animals4.php
http://eflmagazine.com/teaching-resources/grammar-2/pre-intermediate/present-perfect/
Past participle verbs
http://www.englisch-hilfen.de/en/exercises/irregular_verbs/crossword_past_participle.htm
http://www.agendaweb.org/verbs/past-participle.html
For / Since
https://www.englishclub.com/grammar/verbs-m_for-since.htm
http://www.english-grammar-lessons.com/presentperfect/exercise6.swf
http://www.adelescorner.org/grammar/for_since/for-since2.html
http://www.englishexercises.net/yyforsince.html
http://www.montsemorales.com/gramatica/forsince1.htmhttp://www.my-english.edu.pl/index.php?id=29
http://www.english-4u.de/for_since_ex1.htm
http://web2.uvcs.uvic.ca/courses/elc/studyzone/330/grammar/upperf1.htm
Yet, Just, Already
http://www.grammarbank.com/ever-never-just-already-yet.html
http://www.englishexercises.org/makeagame/viewgame.asp?id=3211
http://www.esl-lounge.com/student/grammar/2g7-just-yet-already.php
http://www.curso-ingles.com/practicar/ejercicios/already-just-still-yet
http://www.grammarbank.com/ever-never-just-already-yet-exercise.html
Present perfect vs Simple past
http://www.perfect-english-grammar.com/present-perfect-or-past-simple.html
http://www.englisch-hilfen.de/en/exercises/tenses/simple_past_present_perfect.htm
http://www.englishmedialab.com/Quizzes/intermediate/present%20perfect%20vs%20past.htm
http://www.englishpage.com/verbpage/verbs6.htm
http://gynome.nmnm.cz/fls/dum/aj/22/02_pp_ps.htm
http://www.englishexercises.org/makeagame/viewgame.asp?id=1496
http://www.esl-lounge.com/student/grammar/2g25-george-richards.php
Verb list
http://www.linguasorb.com/english/verbs/most-common-verbs/
http://www.esl-lounge.com/reference/grammar-reference-most-common-irregular-verb-list.php
Haz clic para acceder a irregular+verbs+in+English.pdf
Just to have fun
http://learningapps.org/view455796
https://www.quia.com/cz/475302.html?AP_rand=821730955
https://www.quia.com/cz/335047.html
http://chagall-col.spip.ac-rouen.fr/IMG/didapages/travelling/index.html
https://www.quia.com/cz/310465.html
https://www.quia.com/jg/840403.html
http://www.ompersonal.com.ar/omexercise/tiemposverbales/unit13.htm