Present Simple, Present Continuous and Past Simple

In order to help you studying, I wrote these addresses for you to go, have fun and learn!!

Past Simple exercises:

http://www.isabelperez.com/exer/pastmix.htm
http://www.isabelperez.com/happy/tenses/exercises/past_mistakes.htm
http://www.isabelperez.com/happy/tenses/exercises/past_quest1.htm
http://www.isabelperez.com/happy/tenses/exercises/past_1.htm
http://speakspeak.com/english-grammar-exercises/intermediate/past-simple

Present Simple vs Present Continuous

http://www.youtube.com/watch?v=Bta21cFz9-Y
http://web2.uvcs.uvic.ca/elc/studyzone/330/grammar/simcon1.htm
http://www.ego4u.com/en/cram-up/grammar/simpre-prepro/exercises
http://www.englisch-hilfen.de/en/exercises/tenses/simple_present_progressive.htm