The rst-mode for emacs is very useful but it still lacks some basic features such automatically insert reference links. I wrote my first piece of "real" elisp code to do this, but consider that is only very few lines and probably someone wrote this better.

In the future I plan to ask integration into the mainstream rst-mode.el but for now just copy this into your .emacs/init.el startup file; then try selecting a word (or a phrase) and call the insert-rst-reference function (M-x insert-rst-reference).

(defun insert-rst-reference (url)
  "Inserts footnote link in rst format"
  (interactive "sURL: ")
  (if (use-region-p)
    (let (
      (beg (region-beginning))
      (end (region-end))
      (name (buffer-substring-no-properties (region-beginning) (region-end))))

    (goto-char beg)
    (insert "`")
    (goto-char end)
    (forward-char)
    (insert "`_")
    (deactivate-mark)
    (save-excursion
      (goto-char (point-max))
      (newline)
      (insert ".. _" name ": " url))))
  (error "No region selected!"))

(global-set-key (kbd "C-c l") 'insert-rst-reference)

I binded that to C-c l. Next task is to write a more complex function to autodetect if the cursor is on a word, a selction or something else and behave accordingly.