What about a bat file that copies the address book over to the other computers? If you use robocopy, then it will check the size, time stamps and copy it over only if there something new. If the file is the same size, time stamp then it will not copy it over.
Schedule the bat to run each hour, then you know that everybody has the newest address book.
If I may ask, why dont you run a domain when you have so many computers?