StepGreen
StepGreen is a community site which allows people to share concrete suggestions for reducing their resource consumption. Actions are described along with their impact in terms of reduction of cost, energy, and CO2 emissions, and there's a discussion board for each item. StepGreen allows you to register your commitment to take any of the actions and then to record how often you actually take them. The site displays graphs showing the cumulative savings resulting from the actions you have taken.