Improve your vocabulary

Improve your TOEFL, SAT, GMAT or GRE test vocabulary skills online with the following quizzes.
Practice Sentence Corrections (over 1000 questions)
Practice Antonyms (over 1200 questions)
Practice Analogies (over 2500 questions)
Practice Prefixes, Suffixes and Roots (over 400 questions)

There are also two flash cards available.

GRE word list. 5000 free SAT vocabulary