Available for EC2 instance store volumes. See https://aws.amazon.com/blogs/security/how-to-protect-data-at-rest-with-amazon-ec2-instance-store-encryption/
Also available for EBS volumes. See http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/EBSEncryption.html
You can use a default customer master key (CMK) that is unique to every AWS account or a custom CMK. Data and associated keys are encrypted using the industry-standard AES-256 algorithm. Amazon’s overall key management infrastructure uses Federal Information Processing Standards (FIPS) 140-2 approved cryptographic algorithms and is consistent with National Institute of Standards and Technology (NIST) 800-57 recommendations