While the altruism is a good thing, the reason I come back to the site again and again is that it is intuitive, just like the SAT and the GRE tests are now. As you answer vocabulary questions, FreeRice adjusts to your ability by tracking answers, eventually zeroing in on your word strength and assigning it a number. I scoffed at it initially but as I kept coming back to the site, the same number always came up (though I won’t tell you what it is). This lets you know your progress as your score steadily increases over time.
FreeRice has also added math and Art History (!) multiple choice quizzes to its offerings, but I am still loving the vocab. If you can’t afford to drop four grand on a Kaplan or Princeton prep for the GRE, drop in on FreeRice.