s3 = AWS::S3.new(
:access_key_id => 'YOUR_ACCESS_KEY_ID',
:secret_access_key => 'YOUR_SECRET_ACCESS_KEY')

Reading and Writing to S3
Each object in a bucket has a unique key.
photo = s3.buckets['mybucket'].objects['photo.jpg']

Writing to an S3Object:
photo.write(File.read('/some/photo.jpg'))

Reading from an S3Object:
File.open("/some/path/on/disk.jpg", "w") do |f|
f.write(photo.read)
end

http://docs.amazonwebservices.com/AWSRubySDK/latest/AWS/S3.html

http://aws-portal.amazon.com/gp/aws/developer/account/index.html?action=access-key
https://github.com/amazonwebservices/aws-sdk-for-ruby

http://aws-portal.amazon.com/gp/aws/developer/account/index.html?action=access-key
https://addons.mozilla.org/ja/firefox/addon/amazon-s3-organizers3fox/