Studying using many resources will widen and broaden your insight. Here are some useful websites that will assist you for learning English with exercises:

1. http://www.learnenglish.org.uk/ (British Council)
2. http://www.britishcouncil.org/  (British Council)
3. http://www.teachingenglish.org.uk (Listening/reading comprehension)
4. http://www.bbc.co.uk/ ( listenings)
5. http://englishlistening.com/  (listenings Am En)
6. http://www.richmond.k12.va.us/ (Reading resources)
7. http://yahooesp.englishtown.com/ ( daily lesson)
8. http://es.launch.yahoo.com/ ( video clips)
9. http://www.lyrics.com/ ( songs and lyrics)
10. http://webquest.org/  (Everything about webquest,University of San Diego)
11. http://members.aol.com/ (Exercises)
12. http://www.isabelperez.com/ ( lots of useful links and exercises)
13. http://usuarios.lycos.es/ ( links to exercises)
14. http://eslus.com/ (lots of links to practical exercises)
15. http://www.eslcafe.com/ ( Quizzes, chat ,...)