Two useful links from BBC Learning English, with a grammar reference section and exercises, including audio and video activities:
http://www.bbc.co.uk/learningenglish/course/intermediate/unit-6/session-2/activity-1
http://www.bbc.co.uk/learningenglish/english/course/intermediate/unit-6/session-2/activity-2
http://www.bbc.co.uk/learningenglish/course/intermediate/unit-6/session-2/activity-3
http://www.bbc.co.uk/learningenglish/course/upper-intermediate/unit-25/session-1
