ThemeShock

This lightweight plugin creates a form that is placed by default at the left of the 
content, and is fixed to the top of the page once it gets to it.
Floatin Comments serves as an alternative form to post comments that is very handy 
compared to the traditional comments form. Given that it follows you as you scroll down by 
the page, you can post a comment being at the bottom of the page but also at the 
top.
This plugin is available in 5 different languages, English, Spanish, Portuguese, 
French and Dutch, it will recognize your WordPress installation language and if 
yours is in one of the previews languages you’ll have it automatically 
translated.
<a href='http://www.wpthemeshock.com/' rel="nofollow ugc">By WpThemeShock</a> and <a href='http://www.wpthemegenerator.com/' rel="nofollow ugc"> WpThemeGenerator</a>, <a href='http://www.designshock.com/psd-text-styles/' rel="nofollow ugc">see it in action.</a>
<h3>Features</h3>
<ol>
<li>4 Different Colors</li>
<li>Fixed position when the form gets to the top</li>
<li>Ajax-Powered</li>
<li>Get 100 free sample WordPress Themes</li>
<li>5 Different languages, English, Spanish, Portuguese, French and Dutch.</li>
</ol>

Floating Comments Form Fixed Scroll Position

Floating Comments allows users to post comments to your blog through a fancy form that fallows them as they scroll down.

calliko

The plugin displays floating down the block. In it, you can write the title and body text. 
You can also insert a photo or video to. 
 You can put back the feedback form or links sponsorov.Plagin simple, so long description will not.

float block

Easy to use and truly lightweight plugin to display any type of the information you want. Probably some style customization needed :)

Nice and simple

The plugin displays floating down the block. In it, you can write the title and body text.  You can put back the feedback form or links sponsors.

Floating Comments Form Fixed Scroll Position vs float block