org-auto-clock.el

;; This piece is taken from:
;; http://sachachua.com/blog/2007/12/clocking-time-with-emacs-org/

(eval-after-load'org
  '(progn
     (defun wicked/org-clock-in-if-starting ()
       "Clock in when the task is marked STARTED."
       (when (and (string= org-state "STARTED")
                  (not (string= org-last-state org-state)))
         (org-clock-in)))

     (add-hook'org-after-todo-state-change-hook
               'wicked/org-clock-in-if-starting)

     (defadvice org-clock-in (after wicked activate)
       "Set this task's status to'STARTED'."
       (org-todo "STARTED"))


     (defun wicked/org-clock-out-if-waiting ()
       "Clock out when the task is marked WAITING or PAUSED."
       (when (and (or (string= org-state "WAITING")
                      (string= org-state "PAUSED"))
                  (equal (marker-buffer org-clock-marker) (current-buffer))
                  (<(point) org-clock-marker)
                  (> (save-excursion (outline-next-heading) (point))
                     org-clock-marker)
                  (not (string= org-last-state org-state)))
         (org-clock-out)))

     (add-hook'org-after-todo-state-change-hook
               'wicked/org-clock-out-if-waiting)))