At the first site you can learn how to achieve more miles per gallon of gasoline by adopting driving habits and/or modifying a car. Some of the members have doubled their fuel economy.
http://www.ecomodder.com
Some members modified their vehicles a lot, Here's an image of a modified car:

The owner of the car pictured can get over 70 MPG with it and his driving methods, For example. Such aerodynamic mods are nice and aren't the only ways to get more MPG.
The second website is more about saving energy at home. Think, Mother Earth News-type ideas.
http://www.ecorenovator.org
Austin