JLMARTIN / Cfn-0.14 / t / cfn_yaml / example.yaml 
AWSTemplateFormatVersion: 2010-09-09
Parameters:
  SubnetID:
    Type: AWS::EC2::Subnet::Id
    Description: Subnet to deploy EC2 instance into
  SecurityGroupIDs:
    Type: List<AWS::EC2::SecurityGroup::Id>
    Description: List of Security Groups to add to EC2 instance
  KeyName:
    Type: AWS::EC2::KeyPair::KeyName
    Description: >-
      Name of an existing EC2 KeyPair to enable SSH access to the instance
  InstanceType:
    Description: EC2 instance type
    Type: String
    Default: t2.micro
Mappings:
  AWSRegionToAMI:
    us-east-1:
      AMIID: ami-0b33d91d
    us-east-2:
      AMIID: ami-c55673a0
Resources:
  EC2Instance:
    Type: AWS::EC2::Instance                     
    Properties:
      ImageId:
        !FindInMap                                 # This is an example of the short form YAML FindInMap function
          - AWSRegionToAMI                         # It accepts three parameters each denoted by a hyphen (-)
          - !Ref AWS::Region
          - AMIID
      InstanceType: !Ref InstanceType
      KeyName: !Ref KeyName
      SecurityGroupIds: !Ref SecurityGroupIDs
      SubnetId: !Ref SubnetID
      UserData:
        Fn::Base64:                                # YAML makes userdata much cleaner
          !Sub |
              #!/bin/bash -ex
              yum install -y httpd;
              echo "<html>I love YAML CloudFormation!!</html>" > /var/www/html/index.html;
              cd /var/www/html;
              chmod 755 index.html;
              service httpd start;
              chkconfig httpd on;
      Tags:                                      # Tags are an example of a sequence of mappings in YAML,
        -                                        # each key/value pair is separated by a hyphen
          Key: Name
          Value: CloudFormation Test - YAML      
        -
          Key: Environment
          Value: Development