Links
     
     Present continuous and future exercises:
     http://www.englishclub.com/grammar/verbs-m_future-cp.htm
     http://www.e-grammar.org/present-tense-be-going-to-future/
     http://www.tolearnenglish.com/exercises/exercise-english-2/exercise-english-6874.php
     http://www.bbc.co.uk/worldservice/learningenglish/radio/specials/1530_gramchallenge32/
     
     Present continuous (cross-language comparisons):
     http://en.wikipedia.org/wiki/Continuous_and_progressive_aspects