It reads the (OSX) clipboard and ouput multiple hash of the content. Also if you add a filename as an argument it open the file and hash its content. Windows and Linux port should be straightforward. It paste back the md5 (easy to change) to the clipboard.

hashup

#!/usr/bin/env python -B
#
# Clipboard operations from http://www.macdrifter.com/2011/12/python-and-the-mac-clipboard.html
#
# It will paste md5 by default

import sys
import hashlib
import subprocess

def get_clipboard():
    p = subprocess.Popen(['pbpaste'], stdout=subprocess.PIPE)
    retcode = p.wait()
    data = p.stdout.read()
    return data

def set_clipboard(data):
    p = subprocess.Popen(['pbcopy'], stdin=subprocess.PIPE)
    p.stdin.write(data)
    p.stdin.close()
    retcode = p.wait()

def hash_this(data):
    result = {}
    hashes = ['md5', 'sha1', 'sha224', 'sha256', 'sha384', 'sha512']
    for t_hash in hashes:
        t = getattr(hashlib, t_hash)()
        t.update(data)
        result[t_hash] = t.hexdigest()
    for n in result:
        print("{0:<6} : {1}".format(n,result[n]))
    return result['md5']
target = None

try:
    with open(sys.argv[1]) as f:
        target = "".join(f.readlines())
except:
    target = get_clipboard()

if __name__ == '__main__':
    set_clipboard(hash_this(target))