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.

thenbrent

Every time a page reloads to submit a form, a puppy dies. This plugin is the saviour of puppies.
Grunion Ajax submits a <a href="https://wordpress.org/extend/plugins/grunion-contact-form/" rel="ugc">Grunion Contact Form</a> using Ajax. It makes it super fast for visitors to submit a form.
The Grunion Ajax Javascript file is only loaded if the post or page in question includes the Grunion <code>[contact-form]</code> shortcode, so it’s efficient too.
The only caveat, Ajax submission has not been tested for Grunion Forms included in a widget.

Grunion Ajax

Using Grunion Contact Form? Make form submission slick with Grunion Ajax.

WD3K Ajax Sliding Contact Form vs Grunion Ajax