normalize.rb

class String
  def normalize
    mb_chars.normalize(:kd).gsub(/[^\x00-\x7f]/n, '').to_s
  end

  def normalize_for_display
    mb_chars.normalize(:kd).
    gsub('æ', 'ae').
    gsub('ð', 'd').
    gsub(/[^\x00-\x7f]/n, '').to_s
  end
end

to_utf8.rb

class String
  def to_utf8
    if valid_encoding?
      force_encoding("utf-8")
    else
      force_encoding("utf-8").encode("utf-16be", :invalid => :replace, :replace => "?").encode("utf-8")
    end
  end
end