Today we are fighting evil in general. As you know, advertisements make money. There are several organizations that have sprung up to take advantage of this. Some of them exist for the greater good. For example, B.T.W. (Better the World). In short, sign up, install an advertisement bar on the right hand side of your screen, ignore it, and money gets sent to a cause of your choice. Nice idea I think. There is also a shopping extension that allows for more money to be sent, but I'll let you win my cause some money and let you find out the details.
Also, welcome to the first instantiation of a list of posts about saving the world from your computer for free.