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

http://www.ego4u.com/en/cram-up/grammar/prepositions#exercises

http://www.english-the-easy-way.com/Prepositions/Prepositions_Page.htm

http://www.mansioningles.com/gram34.htm

http://www.ompersonal.com.ar/omgrammar/listadepreposiciones.htm