I am Loving CarrierWave and thought I would share the code I am using on r3dux.net. I have loved its connection information for S3.

photo_uploader.rb

# encoding: utf-8

class PhotoUploader < CarrierWave::Uploader::Base
  # Include RMagick or ImageScience support:
  include CarrierWave::RMagick
  # include CarrierWave::ImageScience
  
  # Choose what kind of storage to use for this uploader:
  if RAILS_ENV == "development"
    storage :file
  else
    storage :fog
  end
  
  version :geo_photo do
    process :resize_to_limit => [900, 500]
  end
  
  version :small_icon do 
    process :thumbnail => [40, 40]
  end
  
  def thumbnail(width, height)
    manipulate! do |img|
      img.thumbnail!(width,height)
    end
  end

  # Override the directory where uploaded files will be stored.
  # This is a sensible default for uploaders that are meant to be mounted:
  def store_dir
    "uploads/#{model.class.to_s.underscore}/#{mounted_as}/#{model.id}"
  end
  
  def cache_dir
    "#{Rails.root}/tmp/uploads"
  end

  # Provide a default URL as a default if there hasn't been a file uploaded:
  # def default_url
  #   "/images/fallback/" + [version_name, "default.png"].compact.join('_')
  # end

  # Process files as they are uploaded:
  # process :scale => [200, 300]
  #
  # def scale(width, height)
  #   # do something
  # end

  # Create different versions of your uploaded files:
  # version :thumb do
  #   process :scale => [50, 50]
  # end

  # Add a white list of extensions which are allowed to be uploaded.
  # For images you might use something like this:
  def extension_white_list
    %w(jpg jpeg gif)
  end

  # Override the filename of the uploaded files:
  # def filename
  #   super + '.jpg'
  # end

end