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.

pvs1984

With horizontal tabs plugin you can add 3 tabs that each of them contains unlimited posts. Each tab shows the featured image and the title of each post
<ul>
<li>option to select the category of post in each tab</li>
<li>option to select the width and the height of feautured image</li>
<li>option to select the number of post in tabs</li>
</ul>

Horizontal Tabs Plugin

Horizontal tabs plugin enable to show unlimited posts in 3 tabs

Floating Comments Form Fixed Scroll Position vs Horizontal Tabs Plugin