If you visit here, you will find out that there is a way to post a badge/button on your site like this
or this or even this
and a tree will be planted in honor of your blog. The tree will be young, and thus produce more oxygen (than the extremely old trees - I don't understand this, I just parrot the information) and hopefully making you and or me feel a little less guilty about carbon emissions. Even though we aren't using paper when we use or rely on computers, we do use energy and produce waste.
According to Carbon Neutral, this programme (Make it Green") started in Germany. The goal is to "reduce carbon dioxide emissions."
There are also buttons for a website and small banners --> example .
Seems rather easy to do, doesn't cost a thing and all you have to do after blogging and putting up a button is send your blog link to CO2firstname.lastname@example.org. They will do the rest.