Shameless Promotion LLC

Add a floating tab to pages on your site which shows additional content (like an ad for your latest product, a contact form, etc) when the user clicks on it. Customize the colors, add images, and add a button link.

Shameless Slide Out

Displays a tab on the side of the screen which slides out to reveal additional content when clicked.

Jick

<a href="http://www.jamesdimick.com/creations/olark-for-wordpress/" rel="nofollow ugc">Now Olark for WordPress!</a>

Shameless Slide Out vs Hab.la for WordPress