Not sure who came up with this idea – but it is great! Freerice.com
You play a vocabulary game, basically … given a word you have to decide which of the choices is closest in meaning to it.
If you get it right, freerice.com donates 10 grains of rice to the United Nations World Food Program.
As you answer correctly the new words become harder and harder. The best score you can achieve is a level 50, but they say on their FAQ that it is extremely difficult getting that … because when you get a word wrong, your score goes down.
Check it out – play a little bit (No registration required) – learn some stuff – and help feed someone in the world.
From their site:
WARNING: This game may make you smarter. It may improve your speaking, writing, thinking, grades, job performance …