The UN World Food Program has created a game to gather food for third-world countries.
In the game, you have to guess the correct synonym for an English word. For non-native speakers it can actually be quite challenging and educational.
Below every question is a different ad, and that way various advertisers sponsor this initiative. I think it's a great idea and gladly link to it. Apart from being a great new, inventive way of helping others, the game is actually a nice use of modern web technologies like CSS and DOM scripting.