This website has a some games/quizzes that students can take.
www.purposegames.com
I am going to use one on the microscope that was already made as a review.
http://www.purposegames.com/game/05c7b310
If students log in they can compete for the high score in the game.
I have found ones for states, part of a sentences and math problems.
You can even make your own games for your discipline.
Hope it helps
Chris