Links

» bilingual dictionary 1	"LEO" - mainly suitable to look up individual words
» bilingual dictionary 2	"PONS" - see short comment above
» monolingual dictionary	"OALD" - mainly suitable to look up collocations and phrases
» a word a day	for (fairly) advanced students - subscribe (it's free) and you'll get a word a day per e-mail, including its pronunciation and example sentences
» pronunciation 1	study the letters of the International Phonetic Alphabet interactively - in order to get the pronunciation of any new English word right
» pronunciation 2	see short comment above
» the Past tenses	explanations and exercises
» grammar etc.	interactive exercises and explanations
» skills 1	the "Learn English Website" of the British Council: grammar explanations and games, listening comprehension exercises, etc., etc.
» skills 2	the "Skillswise Website" of the BBC
» listening comprehension	a large collection of excellent BBC radio programmes, which makes it possible for you to listen to passages of your choice again and again at your leisure - no vocab help though
» literature (etc.)	a brilliant website for students and teachers interested in literature (and more), provided and regularly updated by Mr Fischer
» British humour	some of the information (as usual on Wikipedia) is to be taken with a pinch of salt: most texts are very good - some, on the other hand, may be of rather debatable quality