The Free Green project is pretty interesting. I'm completely in agreement with their mission: "At FreeGreen we hope to encourage progressive building practices by making green home designs free for everyone." What they're doing is providing free house plans which are 'green' -- meaning energy efficient, healthy materials, etc.
You can download the plans for free and take them directly to a builder to arrange construction. They also sell green building products, offer design services, etc.
Despite the zero cost do not confuse this operation with open source. The license these plans are published under do not fit the real open source model. However this is still a very cool service.
UPDATE: I downloaded one of their plans to check out the service.. it's pretty impressive though I have no way to know if these plans are enough to go to a house builder. One thing to be aware of is to download plans you have to register, giving your email address and a couple other bits of identification.
To download plans you're asked to make some selections in a form that describes the sort of house you're looking for. It seems they mean to allow you to search through hundreds of house plans to select the one most fitting your needs. Today there are only two plans available, one for a typical 3-5 person family with a two-car garage, the other a "suburban loft" style home.
The plans download includes three PDF fils: a 'Welcome' package, an energy analysis, and the actual construction plans.
The welcome package is very extensive and gives great information about building a 'green' home and some items to think about. For example there's a really interesting point to ponder about green home financing. It's often thought the price for a green building is higher than a nongreen home, but they suggest a way to reframe this question. The real issue, they suggest, is the cash flow. The vast majority of home purchases are on a mortgage so while your monthly mortgage payment would likely be higher due to the higher purchase price, your other payments (utilities etc) would be lower plus you might easily qualify for a government tax break. The trick is to make the utility cost savings offset the increased mortgage payment.
The welcome package also contains a LEED Certification checklist that's already filled in with the LEED points. LEED? They also include a few pages describing the LEED certification process and how to interpret the checklist.
The energy analysis demonstrates one of the values in potential energy savings. In the plan I downloaded the baseline energy use of a typical house of that size was said to cost over $2,700 per year, however they describe two scenarios of lower energy use with a final cost of either $1,700 per year or $1,000 per year. The latter involves building a photovoltaic system into the house.
The plans document is a detailed walk-through of construction techniques, requirements, LEED certification details etc. There are many pages of engineering drawings showing construction details at all levels from overall floor plan to the inner construction of the walls and more. However since I've never read a set of house construction plans I have no idea whether these are sufficient for a builder to construct a house.
The welcome package suggests the plans are sufficient and that it will help to look for a builder possessing one of these certifications: LEED for Homes, NAHB Green Building Program, or EnergyStar