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Here's your chance to become a philanthropist just by spending little time and having fun while you're at it. FreeRice lets you play a vocabulary game and donate rice at the same time. For every answer you get right, you are donating 20 grains of rice. This is a very nice way to enrich your word power.

Their goals are to: provide free English vocabulary and put an end to world hunger by providing free rice. Rice donations come from advertising sponsors and are done through the United Nations World Food Program.

According to Wikipedia, FreeRice became "Find of the Year" 2007 in the category charity.