Learn a word, give some rice

Here's a neat little game someone posted over at Paperbackswap.com. For every vocabulary word you get right in the game, they donate 10 grains of rice.

According to the FAQ, your playing the game earns money from the advertisers on the site and the money is then used to purchase rice. Fun little game too. I've earned about 1000 grains of rice just now while talking on the telephone to a friend.