http://www.smartgb.com/

http://www.a-free-guestbook.com/

http://www.a-free-guestbook.com/register.php

http://www.freeguestbooks.net/

http://www.thefreesite.com/Webmaster_Freebies/Free_Guestbook_Services/

http://www.guestbooks4free.com/

http://www.123guestbook.com/

http://www.phpjunkyard.com/php-guestbook-script.php

http://www.guestbookcentral.com/

http://www.theguestbook.com/

http://www.multiguestbook.com/

http://en.wikipedia.org/wiki/Guestbook