I haven't visited Free Rice since last spring and, boy, have there been some changes! The site used to only have a vocabulary game, but now it has many others! You can choose from art, chemistry, geography, english, world languages, and math. You can also specify level of difficulty. I've been playing with the geography game (world capitals) this afternoon.
In case you aren't familiar with Free Rice you play the games and for each correct answer, the folks at Free Rice donate 20 grains of rice to the UN World Food Programme. According to the site, 100,938,480 grains of rice were donated yesterday. And this is all FREE for students.
Go ahead, have fun!