Reviewing verb tenses

Present continuous

http://web2.uvcs.uvic.ca/elc/studyzone/330/grammar/pcont1.htm
http://esl.fis.edu/vocab/q21/doing2_r.htm

Past continuous

http://www.english-grammar-lessons.com/pastcontinuous/exercise3.swf
http://www.englishgrammarsecrets.com/pastcontinuous/exercise4.swf

Past simple

http://www.agendaweb.org/exercises/verbs/past-simple-regular
http://www.agendaweb.org/exercises/verbs/simple-past-irregular-1
http://www.english-room.com/pasttense_6a.htm

Present perfect

http://www.adelescorner.org/grammar/pres_perfect/pres_perfect_1.html
https://www.ego4u.com/en/cram-up/grammar/present-perfect-simple/exercises
http://www.agendaweb.org/exercises/verbs/present-perfect-multiple 

Past perfect

http://www.english-grammar-lessons.com/pastperfect/exercise1.swf

http://www.english-grammar-lessons.com/pastperfect/exercise2.swf