Actually, the post by Helpful Harry won't improve your security except for the most simple break in attempts. Since the random seed is attached to the end of the password hash, if you steal the hashed password, you steal the seed.
That means you can write a simple php program to call the pw_check function Harry included from a loop, feeding it dictionary words or random characters.
Of course, if you modified the program to use the seed in a more complicated way, "they" would have to know the new function's operation. But then again, if someone can steal your password database, they can probably steal your website code (or guess it).
