A few other contributors have already posted about concepts that have been put forth by architects relating to green building. For example, William McDonough's work with Cradle to Cradle and use of appropriate, sustainable and sensible materials in architecture. While McDonough is relatively high profile in the architecture world, many many others have done similar work following themes of new urbanism, vernacular architecture and novel materials.
Apart from these efforts though, I'm reminded of a construction method which has always had a small following but may now become more prevalent, particularly in earthquake-prone developing countries. Straw bale construction takes the space in walls normally reserved for sprayed insulation, rolled batts or rigid insulating boards and fills it with stacked straw bales. The straw bales provide far superior insulation to engineered products and use what is a relatively low value, recyclable material. Straw bale homes are not inherently more expensive than standard platform frame construction, except that contractors familiar with the construction method may be harder to find and more expensive. And except for the thick walls and deep sills, the interior of a straw bale home is no different than any other home. There appear to be advantages to straw bale buildings beyond their impressive insulation capabilities. Tests performed by structural engineer Darcey Donovan at University of Nevada, Reno have revealed that straw bale buildings are also excellent at withstanding earthquakes. Donovan's efforts are focused on Pakistan and their rebuilding efforts after the earthquake in Azad Kashmir in 2005, however, her results and subsequent reconstruction and development program might be replicated to great benefit in other areas devastated by earthquakes, particularly agricultural regions. For example, the recent earthquake in Italy is in a region where local (or neighboring state) sources of straw exist and straw bale construction might be a sensible approach to rebuilding efforts. Areas here in America with particularly hot weather and that are earthquake-prone are also (often) centers of agriculture and would be excellent places to encourage new development with straw bale methods.