My Take
Great website for students to review vocabulary words either for general knowledge, building, or SAT prep. You can start on a variety of levels (I think it goes up to 30) and as you progress, it will move you up or move you down if you're not doing well.
How I Use It
I have students use it as vocab review once a week and/or when they have down time after finishing as assignment early before class ends. It requires no set-up time, so I can just tell them to go on it and not have to do anything on my part to set it up. I'm thinking of creating a class chart for how far students get and how many bowls of rice they've donated as a class, to build community around it.