simple present and present progressive

http://www.ego4u.com/en/cram-up/grammar/simpre-prepro

http://www.ego4u.com/en/cram-up/grammar/simpre-prepro/exercises

http://www.englisch-hilfen.de/en/exercises/tenses/simple_present_progressive2.htm

http://www.inglestotal.com/present-continuous-progressive-tense-uso-y-estructura-to-be-ing-el-gerundio-lesson-8/