FreeRice
http://www.freerice.com/index.php
FreeRice is a site that challenges your vocabulary knowledge, while at the same time giving you a way to donate food to needy people around the world. The site has a custom database containing thousands of words at varying degrees of difficulty. There are words appropriate for people just learning English and words that will challenge the most scholarly professors. FreeRice automatically adjusts to your level of vocabulary as you play. It starts by giving you words at different levels of difficulty and then, based on how you do, assigns you an approximate starting level. When you get a word wrong, you go to an easier level. When you get three words in a row right, you go to a harder level.
For each word you get right, the site donates 20 grains of rice to the United Nations World Food Program. The rice is paid for by the advertisers whose names you see on the bottom of your vocabulary screen. The rice is distributed by the United Nations World Food Program (WFP).



