Programmable thermostats can reduce a home's energy expenditure by 10 percent. The next wave of smart thermostats has arrived, and they do the programming for you.
Leading the group is the Nest, which "learns" when you're at home, remembers your temperature habits, and adjusts itself automatically, dialing the temperature up (or down, if it's summer) when it senses you're not around. It's also controllable remotely. [$250; nest.com]