This plugin lets you directly embed video, audio and image files in your WP comments. You can upload and even webcam record your multimedia comments directly from the WP comments template. Just the blog's owner has to be registered at zeec.

X-Comments provides an easy way of adding links to your sidebar that reference the comments you've posted on other blogs/sites. Similiar to the Get Recent Comments plugin but for your comments on other sites. Lightly tested on WP2.0. New version now shows comment previews!

Features:
Wordpress 2.0 compatible, easy install, CSS styling, automatically generates appropriate submit links for 12 bookmarking sites including: Del.ici.ous, Digg, Blinklist, Furl, Reddit, Fark, ...

wp-richcomments lets your blog subscribers attach flickr photos and youtube videos to their comments. The whole interface is written with jQuery, uses thickbox to preview medias and it relies on ajax calls.
In the near future it will be possible to add media files from all the most popular social websites.

A simple guestbook with the comment-functions of wordpress 2.0.
It give two templates for an guestbook with sideabr or without sidebar. I the version it is possible to brake down the entries in pages and other functions.
Possible Themes with Guestbook give it at the follow Link - Guestbook-Templates.