Amazon is experimenting with Amazon Prime Air drones that could feasibly be used as autonomous delivery vehicles. Could make for delivery times as low as 30 minutes. Can carry packages of up to five pounds for round trips as long as 10 miles. To turn this into a commercial service, FAA rules should be in place by 2015. Link
Amazon not the first one to try this. Drones are used in China to deliver packages in the Chinese city of Dongguang. Service is provided by SF Express.