Marcin Pietrzak

Display cool, animated fly-out or fade box with related content.
When a reader scrolls to the bottom of a single post, page, or custom post type, an animate box will be shown allowing the reader to select the previous or random available post or posts in the selected configuration:
<ol>
<li>Just previous</li>
<li>Previous in category</li>
<li>Previous in tag</li>
<li>Random</li>
<li>Related using YARPP (only post/pages)</li>
</ol>

upPrev

Great plugin. Works great, lightweight and doesn't take a lot of resources to manage. 

Great Plugin

Display cool, animated fly-out or fade box with related content.

fozzyluke123

A really simple to use plugin that will create a floating element that either displays login/ register or logout/profile, depending on whether the user is logged in. Fully customisable colors, links and properties.

Floating Login

Floating login/ register element that sticks to the top of the screen and changes depending on user login state.

upPrev vs Floating Login