One component of this that I'm a big fan of has been the movement to incorporate green roofs into especially city dwellings. This can mean anything from not using the typical black tar roofs (which hold in heat, contributing to the urban heat island effect) to creating almost a garden on the roof. This can be done on anything from a small home to skyscrapers.
An example of this is the City Hall rooftop in Chicago. Chicago has become known as a center for green technology and roofs are no exception. For instance, a $5,000 grant from the city is available for anyone who wants to create a green roof.
Lately, the push for usage of this option nationally has grown stronger. A blog called WorldChanging has a pretty extensive rundown here. They say:
Green roofs add so many benefits to a building and its surrounding area, it's astonishing that more roofs aren't green at this point... Although green roofs cost more up front to install than regular roofs, the savings that they accrue over the years quickly pay off.There are of course future maintenance concerns and concerns about the roof's durability, but to me, the idea of making green roofs more commonplace is a no-brainer. I have to think that the opportunity to lounge on a garden in the sky would be pretty attractive to most people.
For further information or if you're interested in becoming an advocate in your city, you could consider joining the "Green Roofs for Healthy Cities" campaign.
I have the feeling that this is an idea that will only continue to grow.