Amazon S3 service is currently along with CloudFront.
Update: Amazon just confirmed that they have issues with Amazon Simple Storage Service in US. From the health dashboard:
1:40 AM PST We are currently experiencing very high error rates in our West coast facility. We’ll be providing an update shortly.
2:07 AM PST We’re in the process of taking corrective action based on our current assessment of the issue and will provide more information regarding status as we have it.