I’m a fan of using advertising in different ways. People are quite media literate these days, so old style advertisements are quickly losing their affect.
One thing that always works to get people is the feeling of doing some good. There are a couple of sites that have harnessed that (in partnership with advertisers). You should look at how they’ve set up this concept. Often, people will click through just to be certain that the advertisers contribute money, and that’s when you can appeal to them right from your own site.
One example is here: