Note to self for web sites hosted in S3 buckets with DNS in Route 53. Rather than create a CNAME, use an alias record. Alias records are Route 53 specific pointers to an ELB load balancer, an S3 web site bucket or another resource record set in the same zone. For the case of an S3 bucket, it will point to the IP of the bucket. By using an Alias record, you save the extra lookup a CNAME would cause. Queries to alias records mapped to S3 buckets are free.
If creating the record in the Route 53 console, add a record set of type A or AAAA, mark it as an ALIAS record and then choose from available buckets, ELB instances or other record sets for the alias target.
Have a look at Amazon's documentation for more information.