Subset and permutations without explicit recursion. The permutation implementation uses a fixed point combinator.

subset-permutation.ss

(define (subsets l)
  (foldl (lambda (x y) 
           (foldr (lambda (u v) (cons (cons x u) (cons u v)))
                  '() y))
         '(()) l))

(define permutations
  (lambda (l)
    (((lambda (f)
        ((lambda (x) (f (lambda arg (apply (x x) arg))))
         (lambda (x) (f (lambda arg (apply (x x) arg))))))
      (lambda (f)
        (lambda (l acc)
          (if (empty? l) (list acc)
              (foldr (lambda (o w)
                       (foldr cons w
                              (f (filter (lambda (t) (not (= t o))) l) 
                                 (cons o acc))))
                     '()
                     l))))) l '())))