Agendaweb is a basic website for independent students where you'll find lots of interesting graded exercises to work on every aspect of English with grammar, vocabulary, reading, listening, even songs! It's really well organized and includes all levels. But don't try to do an exercise if you don't know the corresponding grammar, it's a waste of time! Try an easier exercise.
I specially recommend it to parents, it's great to practise with your children and see how easily they learn English!
