This is the code Samuel refers to. It is awesome. I use it less and less ;) by which I mean everytime I use it is one less time I ever have to use it.

;; http://endlessparentheses.com/ispell-and-abbrev-the-perfect-auto-correct.html

(define-key ctl-x-map "\C-i" 'endless/ispell-word-then-abbrev)

(defun endless/ispell-word-then-abbrev (p)

  "Call `ispell-word'. Then create an abbrev for the correction made.

With prefix P, create local abbrev. Otherwise it will be global."

  (interactive "P")

  (let ((bef (downcase (or (thing-at-point 'word) ""))) aft)

    (call-interactively 'ispell-word)

    (setq aft (downcase (or (thing-at-point 'word) "")))

    (unless (string= aft bef)

      (message "\"%s\" now expands to \"%s\" %sally"

               bef aft (if p "loc" "glob"))

      (define-abbrev

        (if p global-abbrev-table local-abbrev-table)

        bef aft))))