Amazon CloudFront delivers your content using a global network of edge locations. Requests for your objects are automatically routed to the nearest edge location, so content is delivered with the best possible performance.
geek footnote: the bigass images on dopplr's new city pages are served from Amazon's Cloudfront CDN. And it was really easy.
Very happy about Amazon CloudFront, about 100-120 msec for static files like images, js, etc... in Spain (going to France). Faster than S3