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There isn't a specific pre-canned AMI, but you can install node.js in an instance based on a suitable AMI and then shrink-wrap your new build into an AMI of your own.
There are likely community supported AMIs that include Nodejs, however you'll probably get better mileage using a tool like OpDemand. They offer a number of different Node.js stacks that you can deploy on AWS for free. If you pair OpDemand's free account with a t1.micro, you can host and manage the whole thing for free!