Want to challenge your vocabulary and help end world hunger? Go to www.freerice.com and take a look. Free Rice is really fun; every word answered correctly provides 20 grains of rice to the program.
The rice is paid for by the advertisers on the site and distributed by the United Nations World Food Program. If you are interested in learning more about hunger or poverty take a look at www.poverty.com which is a sister site of www.freerice.com
The game is challenging and has 50 levels of vocabulary - I have made it to level 35 so far.