foo.rb

#!/usr/bin/ruby                                                                 
require 'net/http'                                                              
                                                                              

META_BASE = "/2008-02-01/meta-data"                                            

def server
  @server ||= Net::HTTP.new("169.254.169.254")                                  
end
                                                                                
def get_data(request_uri)                                                       
  request   = Net::HTTP::Get.new(request_uri)                                   
  response  = $http.request(request)                                            
  return response.body                                                          
end                                                                             
                                                                                
get_data(META_BASE).split.each do |item|                                       
  data = get_data("#{$meta_base}/#{item}")                                      
  puts "#{item} => #{data}"                                                                                                                                                               
  puts "----------------"                                                       
end

meta.rb

require 'net/http'
require 'open-uri'
@metadata=Hash.new
base="http://169.254.169.254/2008-02-01/meta-data/"
puts URI(base).open.read
puts '------------\n'
%w(reservation-id
security-groups
public-ipv4
ami-manifest-path
instance-type
instance-id
local-ipv4
local-hostname
ami-launch-index
public-hostname
hostname
ami-id
instance-action
).each do |key|
  @metadata[key]=URI("#{base}#{key}").open.read
end


@metadata['zone']=URI("#{base}placement/availability-zone}").open.read
@metadata['ssh-key']=URI(base+'public-keys/').open.read.split('=').pop

# iterate over block devices
#block-device-mapping/
@metadata['block-devices']={}
URI(base+'/block-device-mapping/').open.read.each do |block| 
  @metadata['block-devices'][block]=URI("#{base}/block-device-mapping/#{block}").open.read
end

print @metadata.inspect