(defn lazy-input
  "Returns a lazy sequence of characters from an input stream or Reader."
  [input-stream]
  (let [step (fn step []
               (let [c (.read input-stream)]
                 (when-not (== c -1)
                   (cons (char c) (lazy-seq (step))))))]
    (lazy-seq (step))))

Taken from here http://groups.google.com/group/clojure/msg/1590311bac972d15, useful if you can not (or do not want to) line-seq file (e.g. when whole file is one big line).

Lazy characters input

Clojure