This is an old thing, but just in case someone hasn’t heard of it:
It’s a WFP website/programme with a few subject tests. For each question you answer correctly WFP sponsors (the ad people, so turn of Adblock!!!) donate 10 grams of rice.
It is actually a very useful site for students learning English - I personally use it all the time to build/refresh/test my vocabulary - aaaaand it benefits the world. So go go go go go