Present continuous and past simple

Present  continouns lesson
http://www.englishpage.com/verbpage/presentcontinuous.html

Present continuous practice

http://www.eclecticenglish.com/grammar/PresentContinuous1F.html

Present continuous excercise
http://www.perfect-english-grammar.com/present-continuous-exercise-6.html

http://www.englisch-hilfen.de/en/exercises/tenses/present_progressive_auxiliaries.htm

Videos
http://www.youtube.com/watch?v=EU_OC-j6pjY

Simple past
Lesson
http://www.ego4u.com/en/cram-up/grammar/simple-past
http://www.englishpage.com/verbpage/simplepast.html

Practicce
http://www.englishgrammarsecrets.com/pastsimple/exercise1.html

Excercise
http://www.perfect-english-grammar.com/past-simple-exercise-7.html

Videos

http://www.youtube.com/watch?v=Qp70cSK9hxo