FreeRice.com

Free Rice

This is great. Improve your vocabulary and donate rice to the United Nations World Food Program (WFP).

Really simple interaction. And it’s double compelling: you want to play more (if you’re a word geek) and it’s a really easy way to give to charity. The rice is all paid for by the advertisers on the site.

Not 100% original. The click and give mechanic paid for by advertisers has been done a few times before, but I’m sure it’s fresh to lots of people. And it’s still a winner.