Check out this great article on ways to save gas from consumer reports. Yup, idling is on the list! All the other advice is great, too.
Avoid idling for long periods
Think of it this way: When you’re idling, your car is getting zero miles per gallon. When we let a Buick Lucerne, with a V8, idle for 10 minutes while warming up, it burned about an eighth of a gallon of gas. A smaller engine would probably burn less, but idling still adds up over time. As a rule, turn off your engine if you expect to sit for more than about 30 seconds. An engine warms up faster as it’s driven anyway.