Using English is particularly useful for its phrasal verb dictionary, idioms dictionary and ask a teacher forum.  They have quizzes about phrasal verbs and if you have any questions they have special forums for phrasal verbs and idioms.  If you’ve heard an expression in a film or read something in a book that you just can’t understand, ask the helpful people at Using English.  I post there sometimes, too!

The BBC is possibly one of the richest sources of high-quality, free English learning material on the Internet.  Their Learning English site has so many sections I really can’t talk about all of them here (although I will say Words in the News is a very good place to start).  Skillswise has excellent sections on spelling, reading, and writing.  Their Video Nation site has interviews with real people and a short quiz afterwards to see if you...