MFT Mac salt
MFT Mac Salt is a simple but very fast Python Script to run against user logon salted password hashes. After version 10.4 of Mac OS X all user passwords are pre salted SHA1 hash of the password so even a blank password creates a different hash.
MFT Salt deconstructs the users password file, then applies this information to try and see if the password is blank if it is not it will go on and attempt a dictionary attack against the hash.
All you need to do it copy out the users hash file and then pass this to the Python Script via a Mac OS X Terminal Window or the Windows Command Prompt along with the dictionary you wish to use.
As this is a script I have zipped up the download to, hopefully, stop virus checkers blocking it. Also as this is a script you can read it first to make sure what it is doing prior to running.