A cute little dehasher.

dehash.py

import hashlib, sys

words = open('/usr/share/dict/words', 'r').read().splitlines()
hashes = [ hashlib.md5(w).hexdigest() for w in words ]
dictionary = dict(zip(hashes, words))

try:
    print dictionary[sys.argv[1]]
except:
    print "Could not decrypt hash."