CentOS, Amazon EC2, and EBS AMI

Actually, your best bet is probably the Amazon Linux AMI: http://aws.amazon.com/amazon-linux-ami/

It's CentOS/RHEL under the hood, so you can use all the CentOS RPMs and such, but you get Amazon's tweaks and improvements so it runs even better in EC2.

The best practice is to either use the official image provided by the distro (CentOS started to provide these recently). Or to build your own image directly from a kickstart file. Either using a tool like ami-creator, or directly running a kickstart based install on EC2.

We recently wrote a blog post showing how this can easily be done on EC2: http://www.comodit.com/2012/11/26/kickstarting-on-ec2/