Found this site on psfk today. It's a cracking idea.
You choose - from multiple choice answers - the word which best matches the meaning of the specified word. (I think that's a suitably clumsy explanation...) And for each one that you get right, ten grains of rice are donated via the United Nations presumably to the hungry somewhere.
A brilliant example of advertising helping to achieve something both imaginative and really positive. And incredibly compelling for those that fancy themselves as having a bit of an extensive vocabulary.