I agree with Scott- Geothermal isn't always the best answer because it has a high cost. Capstone Homes is a medium sized builder at the Delaware Beaches, and we use Energy Star windows, tankless w/h, blown fiberglass insulation- these things get our homes with a consistent HERS score in the 60's (a HERS score of 85 is Energy Star).
Geothermal is absolutely the way to go in terms of efficiency- but the cost is high. In Delaware, it is hard to make solar or wind work, but that can vary greatly state-to-state because of the rebates and incentives offered by the state government.
Our link can teach you about some of the things we put into our homes.