(defun insert-by-key (o os key)
   (cond ((endp os) (list o))
         ((< (cdr (assoc key o))
             (cdr (assoc key (first os))))
          (cons o os))
         (t (cons (first os)
                  (insert-by-key o (rest os) key)))))

(defun isort-by-key (os key)
   (if (endp os)
       nil
       (insert-by-key (first os)
                      (isort-by-key (rest os) key)
                      key)))

(isort-by-key
 '(((name  . "map")
   (weight . 9)
   (value  . 150))
  ((name   . "compass")
   (weight . 13)
   (value  . 35))
  ((name   . "water")
   (weight . 153)
   (value  . 200))
  ((name   . "sandwich")
   (weight . 50)
   (value  . 60))
  ((name   . "glucose")
   (weight . 15)
   (value  . 60)))
 'value)