Finding good information on the net is a very time consuming task. Following are some interesting links that I have found and used. It includes everything from grammar, quizzes, idioms, e-mail pals, chat, and ideas on everything related to teaching, and much, much more. James Rainville's page will provide information on grammar, games, quizzes, activities, e-mail pals, chat, and anything you might think of. Be patient, and you can find some good stuff.
Students can also do quiz to identify their weaknesses.