DoGoodHQ.com offers a downloadable plug-in which will hide those pesky ads you hate and replace them with "thoughtful green related initiatives, philanthropic calls for action, and health and wellness ideas instead." And if that doesn't make you feel good, then I hope this will: they will donate 50% of their profits back into green initiatives, charities and non-profit orgs. And if that doesn't make you feel good... well you might just be dead inside.
My only complaint (and I've chatted with their reps about this via Twitter: @dogoodhq), is that they currently don't support Chrome, which is my default browser. They do however support all the major players (FF, IE and even Safari for all you Mac fanboys).
Surprisingly, after several months online, they have fewer than 2000 downloads (which is kinda sad). I hope more people will catch wind of the good work they are doing and spread the word.
I encourage you to download their plug-in and help save the world click-by-click.