d3wp

This plugin generates nice jQuery powered sliding contact form in the left border of your WP blog. 
Contains client side validation and ajax powered mailing, so no page refresh is required. 
Admin section allows you to configure all form labels including error messages and form status messages.
<h3>Feedback</h3>
http://www.webdev3000.com/

WD3K Ajax Sliding Contact Form

An Ajax powered sliding contact form, based on Contactable (jQuery Plugin) By Philip Beel.

Vladimir Prelovac

WP Wall is a “Wall” widget that appears in your blog’s sidebar acting as a cool shoutbox for your visitors.
The comment will appear in the sidebar immediately, without reloading the page.
All comments are internally handled by WordPress so that means you have normal comment moderation, SPAM protection and new comment notification.
WP Wall is fully customizable with a CSS file and included graphics.
WP Wall features: 
* Global commenting “Wall” 
* Comments are handled entirely by WordPress 
* RSS Feed for the Wall 
* Smilies 
* Instant delete for admin 
* Option to display HTML and make links clickable 
* Navigation through pages 
* Interactive Wall: It can automatically refresh turning into a chat
Plugin by Vladimir Prelovac. Also check out <a href="https://managewp.com" rel="nofollow ugc">ManageWP</a>.
<h3>License</h3>
This file is part of WP Wall.
WP Wall is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.
WP Wall is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with WP Wall. If not, see <a href="http://www.gnu.org/licenses/" rel="nofollow ugc">http://www.gnu.org/licenses/</a>.

WP Wall

"Wall" widget that appears in your blog's sidebar acting as a cool shoutbox for your visitors.

WD3K Ajax Sliding Contact Form vs WP Wall