As I pointed out some posts ago, there are lots of wonderful teachers who share their experience and their hard work on the web. Isabel Pérez Torres is one of those, and her site, Isabel's ESL is one of the most impressive web pages I've ever known. I strongly recommend it to both teachers and students.
This is an opportunity to thank her job and also to post one of her exercises: Lemon Tree Song
Don't miss the video. It's not hers (but I discovered it in her blog)
Lemon Tree Video
By the way, Lemon Tree is a song by Fool's Garden, a German pop group formed in 1991.