Does EC2 support AES-NI instructions? If so, is there a particular instance type?

When this answer was first written, many instance types did, but not all. http://aws.amazon.com/ec2/instance-types/ currently (2015-Dec-10) says "Intel AES New Instructions (AES-NI): Intel AES-NI encryption instruction set improves upon the original Advanced Encryption Standard (AES) algorithm to provide faster data protection and greater security. All current generation EC2 instances support this processor feature."

from my testing, no. all of the ec2 instances I've tested use intel E5xxx or X5xxx cores, which don't support AES_NI. You'll need E7s for that. maybe we'll get lucky when new hardware trickles in.....