This isnt a GuestBook plugin for WordPress or even a hack made for WordPress....but since im a total newb at WordPress and couldnt get any of the plugins to work....i went and found this script to use on my site for a GuestBook. And it works rather well, im happy with it. You can view it at my site http://www.mythdranner.com/press/ for now thats where my WordPress script is till i get it set the way i want it, then i will move it to my main site.
You can download the script for the guestbook at :
Enjoy! And if you go to my site to see it in action the link is at the top of the banner marked gbook :)