The folks over at Joystiq have my attention to a free game that both helps your brain and starving people in developing nations.

Freerice is a game where you are presented with a word and four other words, one of which means the same thing as the first word. For every correct match you make, the site's sponsors will donate ten grains of rice through the united nations to help ease hunger. As you get correct answers the words get harder, but if you start missing answers the difficulty eases off, this means you should be challenged, but still be able to get answers right.

The game is also pretty addictive, I can't seem to break through the level 41 layer.