Build your vocabulary and feed the hungry

Free Rice offers a multiple-choice vocabulary quiz — for every word you get right, they “donate 20 grains of rice through the United Nations to help end world hunger”. It adjusts to your abilities — if you get a word wrong, it’ll bump you down to an easier level; if you get three words in a row correct, you move up to a harder level. There are 50 levels, but they say that “it is rare for people to get above level 48″.