This is a nifty (wow, am I a 70s girl or what??) website where you can take a free vocabulary quiz and if you get it right, 20 grains of rice will be donated to those less fortunate than you through the World Food Programme. You start with a simple word and it gets progressively more difficult. I was able to get several words correct and I know YOU can, too!

http://www.freerice.com/index.php