FreeRice

According to the United Nations, a child dies every 10 seconds from hunger related causes. Which is one good reason why you must stop off here and take part in some of the quizzes, which enable the site to donate grains of rice for each answer you get correct.

The arrangement is paid for by banner advertising, but if you're running AdBlock you won't see it anyway.

Since its inception, the site has expanded from the first English vocabulary quiz and now offers a range of subjects including art, chemistry, math, language learning and geography. The quizzes have many levels to choose from, and up at the higher end they are seriously tough. And that means, anyone can learn something here while donating to a good cause. And you will be challenged, because as you successfully answer tougher questions, the quizzes automatically respond by increasing the difficulty of the next ones.

Does it make a difference? Apparently so. Just spending a few minutes here will let you donate two or three hundred grains of rice, and the site gets enough visitors to increase that figure into the hundreds of millions of grains of rice per year.

This is one of the must-bookmark sites for anyone who has a coffee break. You can make a donation every day without leaving your cubicle, thus pleasing your boss, who would prefer you never saw the light of day while at work. Everyone wins.