Assignments, Quizzes, and Games

Boggle World has a lot of free resources for English as a Second Language teachers, including crosswords, flashcards, word searches, and a comprehensive resource directory.

Abroad Languages offers free language games.

Better English offers free online exercises and quizzes, as well as an English Lessons mailing list for teachers and students.

At Unwords.com you can make up words for those hard to express things and ideas in your head.