(defun totd ()
  (interactive)
  (with-output-to-temp-buffer "*Tip of the day*"
    (let* ((symbols (loop for s being the symbols
			  when (or (commandp s) (user-variable-p s))
			  collect s))
           (symbol (nth (random (length symbols)) symbols)))
      (princ
       (concat "Your tip for the day is:\n========================\n\n"
               (cond ((commandp symbol)
		      (concat (describe-function symbol)
			      "\n\nInvoke with:\n\n"
			      (with-temp-buffer
			       (where-is symbol t)
			       (buffer-string))))
		     ((user-variable-p symbol)
		      (describe-variable symbol))))))))