Create a new file from the current region.

extract-region-to-file.el

(defun extract-region-to-file (filename)
  "Extract text in the region to a file"
  (interactive "FExtract to file: ")
  (save-excursion
    (if buffer-read-only
	(copy-region-as-kill (region-beginning) (region-end))
      (kill-region (region-beginning) (region-end)))
    (find-file filename)
    (end-of-buffer)
    (unless (= (buffer-size) 0)
      (newline))
    (yank)))

(define-key global-map  (kbd "C-x X")   'extract-region-to-file)