Guestbooks.cc
Provides free remotely hosted guestbooks with an abundance of features that are unique to a guestbook service. Features include complete customization, entry moderation, word filter, IP banning, smilies, cool editor, spam filter, flood filter, and 'instant' posting. Website owners can manage their guestbook's entries from a web control panel as well as all their settings. The guestbook can also be tracked through an XML feed available from the web control panel.

AnvilBook.com
Here, you can sign up for a free guestbook for your Web site. AnvilBook.com guestbooks are easy to use and offer lots of features including time zone and date formatting and customizable body background, link and text color.

UltraGuest.com
Free fully customizable guestbook service with unlimted guestbook entries, support for RSS, spam protection, up to 3 custom fields and private messages.

Freeguestbooks.net
A great free remotely hosted guestbook service that's packed with a ton of useful features, including: a customisable guestbook interface, private messaging, user and IP address banning, usage of smilies (emoticons), entry editing, site recommendation, etc.

Smartgb.com
Here's a quality and well-maintained free guestbook service for Webmasters. Smartgb.com includes over 60 predefined themes to select from, so you can customise the guestbook to match your site.

123Guestbook
Free guestbook provider with tons of features, such as replying, editing and deleting messages, thank-you email, email on new entry, scroller with last message to put on your website, and lots more.

eFreeGuestbooks
This is a good place to go if you're looking for a free guestbook for your site. eFreeGuestbooks offers remotely hosted, ad-supported guestbooks that are highly customizable. Features here include bad word filtering; IP and E-mail banning; new entry alerts and over 30 smilie faces to choose from.

Web Site Goodies Guestbooks
Click on the "Tools" link near the top of the page to access WebSiteGoodies' free guestbook service. Here, you can easily set up a guestbook that offers lots of features and can be customized to match your site.