Irregular verbs exercises

Lista de verbos irregulares agrupados por sonido:
http://www.sherton.com.ar/irregulares/fonetico1.htm

http://www.englisch-hilfen.de/en/exercises_list/verbs.htm
http://www.englishexercises.org/makeagame/viewgame.asp?id=3494
http://www.ego4u.com/en/cram-up/grammar/irregular-verbs
http://www.englishpage.com/irregularverbs/interactiveirregularverbs1.htm

Past simple past continuous

http://mbonillo.xavierre.com/grammar/3eso.html