PRESENT SIMPLE VS PRESENT CONTINUOUS

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

http://web2.uvcs.uvic.ca/elc/studyzone/330/grammar/simcon.htm

http://www.englishpage.com/verbpage/verbs1.htm

http://www.isabelperez.com/happy/tenses/exercises/present_6.htm