Back in May, Google announced a new tool they were developing called PowerMeter. The concept behind PowerMeter was simple. If you really want to save energy, you need to get feedback on your energy usage. Rather than trying to puzzle out all the things you tried in a month, it would be much more helpful to get immediate feedback.
If you turn off a light, how much energy did you save? Did adjusting your thermostat make a huge difference last night? Are you doing better this year than you were last year? Google PowerMeter could tell you.
PowerMeter was designed as an iGoogle gadget that would work with new infrastructure from our energy companies called the smart grid. Well, that's fantastic, but most of us don't live anywhere near a smart grid. Google's solved that problem by partnering with a device maker. TED 5000 energy meters from Energy Inc can be purchased by ordinary consumers interested in saving energy. The devices start at around $200, but I imagine they'd pay for themselves after a while.