From the Poverty.com folks, you can now improve your vocabulary while and feed the world at the same time. FreeRice.com has been able to sell advertisement on their site in exchange for your eye balls while you improve your vocabulary.
After starting just a few weeks back (October 7), FreeRice.com has already donated 537,163,380 grains of rice. Now I don't know how many grains of rice are in a cup, but it sounds impressive. For every correctly identified definition, 10 grains are donated -- perhaps with some traffic growth, FreeRice.com could charge advertisers more, so 15 grains of rice could be donated for every correct answer.
It's time you do your part -- work on your vocabulary and help feed the world.