Kevin Langley Jr.

Add widgets on a post by post basis by using a new interface directly on the post edit screen.
Filter to set the post types the Post Widgets plugin should load on post_widget_post_types

Voce Post Widgets

A better interface for managing your widgets.

Daniel Ostman

Separator Widget inserts a horizontal rule ( <code><hr></code> ) or a custom div ( <code><div class="my-separator"></div></code> ) in your widget area. Each widget can be set to one of those options.
No extra styling is added so you are free to style them however you want it. 
Add your custom <code>hr</code> styling to your CSS or use <code>.my-separator</code> if you prefer that option.
Free and easy to use!
<a href="http://www.danielostman.se/" title="Visit WordPress developer web site" rel="nofollow ugc">More info about the WordPress plugin developer</a>

Separator Widget

A widget that inserts a horizontal rule or a custom div.

Voce Post Widgets vs Separator Widget