Dictionaries:
http://dictionary.cambridge.org/
http://www.merriam-webster.com/
Listening:
BBC Sounds
Grammar and Vocabulary:
http://www.bbc.co.uk/worldservice/learningenglish/
Pronunciation:
http://www.oddcast.com/home/demos/tts/tts_example.php?sitepal
http://www.shiporsheep.com/