Below are some of the useful links that you might make use of for the sake of improving your English:

British Council

http://www.britishcouncil.org/learn-english

BBC Learning English

http://www.bbc.co.uk/worldservice/learningenglish/general/talkaboutenglish/

English Club

http://www.englishclub.com/speaking/

English-English Dictionary

http://www.merriam-webster.com