I was recently reading about how in the Netherlands you can get a credit card where, instead of earning miles or the like, your purchase helps offset carbon emissions. It's called Greencard Visa and, at this point, is only available to residents of the Netherlands.
For every purchase made, new trees are planted or other methods of offsetting carbon emissions are taken in order to make erase the cardholder's climate footprint.
An American company, called Bright Planet, is set to launch a similar program in May where "points" earned are invested in new clean energy projects. Bright Planet's web site leaves much to be desired, but this article helps sort things out.
If you're looking for a more recognizable bank card, later this year Bank of America will be offering its consumers an eco-friendly credit card. For every dollar spent on this new card, Bank of America will make a contribution to an environmental organization to invest in greenhouse gas reduction projects.